GMAT(VERBAL)逻辑推理模拟试卷20含答案解析

GMAT(VERBAL)逻辑推理模拟试卷20

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逻辑推理

1.The Sumpton town council recently voted to pay a prominent artist to create an abstract sculpture for the town square. Critics of this decision protested that town residents tend to dislike most abstract art, and any art in the town square should reflect their tastes. But a town council spokesperson dismissed this criticism, pointing out that other public abstract sculptures that the same sculptor has installed in other cities have been extremely popular with those cities’ local residents.

The statements above most strongly suggest that the main point of disagreement between the critics and the spokesperson is whether(B)

A. it would have been reasonable to consult town residents on the decision

B. most Sumpton residents will find the new sculpture to their taste

C. abstract sculptures by the same sculptor have truly been popular in other cities

D. a more traditional sculpture in the town square would be popular among local residents

E. public art that the residents of Sumpton would find desirable would probably be found desirable by the residents of other cities

解析:Argument Construction

Situation After the Sumpton town council voted to pay a prominent sculptor to create an abstract sculpture for the town square, critics protested the decision. A town council spokesperson responded to the critics.

Reasoning What do the critics and the spokesperson mainly disagree about? The critics argue that Sumpton residents dislike most abstract art and that art in the town square should reflect their taste. Since the critics are protesting the town council’s decision, they are clearly inferring from the residents’ general attitude toward abstract art that the residents will dislike the specific sculpture the prominent sculptor will create. The spokesperson replies by arguing that in other cities, sculptures by the same sculptor have been very popular with local residents. The spokesperson implicitly infers from this that the sculpture the prominent sculptor will create for Sumpton will be popular with Sumpton residents—and therefore that the critics are mistaken.

A Neither the critics nor the spokesperson mentions consultation with the town residents on the decision.

B Correct. As explained above, the critics raise points implicitly suggesting that the residents will dislike the sculpture, whereas the spokesperson responds with a point implicitly supporting the opposite conclusion.

C The critics could concede that the sculptor’s work has been popular in other cities, but nonetheless hold that Sumpton residents have different tastes from those of the other cities’ residents.

D The spokesperson gives no indication regarding the attitudes of Sumpton residents regarding traditional sculpture.

E It may be that neither the critics nor the spokesperson holds this view. The spokesperson may hold that Sumpton residents are easier to please than residents of most other cities, whereas the critics may hold that Sumpton residents are far more traditional in their tastes than other cities’ residents.

The correct answer is B.

2.Jay: Of course there are many good reasons to support the expansion of preventive medical care, but arguments claiming that it will lead to greater societal economic gains are misguided. Some of the greatest societal expenses arise from frequent urgent-care needs for people who have attained a long life due to preventive care.

Sunil: Your argument fails because you neglect economic gains outside the health care system: society suffers an economic loss when any of its productive members suffer preventable illnesses.

Sunil’s response to Jay makes which of the following assumptions?(D)

A. Those who receive preventive care are not more likely to need urgent care than are those who do not receive preventive care.

B. Jay intends the phrase \

C. Productive members of society are more likely than others to suffer preventable illnesses.

D. The economic contributions of those who receive preventive medical care may outweigh the economic losses caused by preventive care.

E. Jay is incorrect in stating that patients who receive preventive medical care are long-lived.

解析:Argument Construction

Situation Some of the greatest societal expenses arise from frequent urgent-care needs for people who have reached old age thanks to preventive medical care. But society also suffers economic loss when my of its productive members suffer preventable illnesses.

Reasoning What is Sunil assuming in his argument that Jays argumentfailst’Jay implies that by helping people live longer, expanding preventive medical care may actually increase the amount of urgent medical care people need over the course of their lives, and that societal expenses for this additional urgent care may equal or exceed any societal economic benefits from expanding preventive care. Sunil responds by implying that expanding preventive care would allow society to avoid economic losses from lost productivity caused by preventable illnesses. In order for Sunil’s argument to establish that Jay’s argument fails, the potential economic benefits that Sunil implies would arise from expanded preventive care must be greater than the economic losses from the increased need for urgent care that Jay points out.

A This is not an assumption that underpins Sunil’s suggestion that the societal economic benefits from expanded preventive care may exceed any resulting economic losses from urgent care.

B If Jay intends the phrase \

3.Boreal owls range over a much larger area than do other owls of similar size. The reason for this behavior is probably that the small mammals on which owls feed are especially scarce in the forests where boreal owls live, and the relative scarcity of prey requires the owls to range more extensively to find sufficient food.

Which of the following, if true, most helps to confirm the explanation above?(B)

A. Some boreal owls range over an area eight times larger than the area over which any other owl of similar size ranges.

B. Boreal owls range over larger areas in regions where food of the sort eaten by small mammals is sparse than they do in regions where such food is abundant.

C. After their young hatch, boreal owls must hunt more often than before in order to feed both themselves and their newly hatched young.

D. Sometimes individual boreal owls hunt near a single location for many weeks at a time and do not range farther than a few hundred yards.

E. The boreal owl requires less food, relative to its weight, than is required by members of other owl species.

解析:Argument Evaluation

Situation The small mammals on which owls prey are relatively scarce in the forests where boreal owls live. That is why boreal owls range more extensively than do other, similarly sized owls in search of food.

Reasoning Which choice, if true, would most help confirm the proposed explanation? One way to confirm an explanation is by finding further information that one would expect to be true if the explanation is valid. If the explanation in the passage is valid, then one would expect that variations in the population density of available small-animal prey for boreal owls would be accompanied by variations in the ranges of the boreal owls. Naturally the population density of available small-animal prey is likely to be affected by how plentiful food is for those small animals.

A The comparison between different groups of boreal owls is not relevant to the comparison between boreal owls and other owls.

B Correct. This indicates that abundance of food for the boreal owls’ small-animal prey in an area (and therefore abundance of small animals in that area) correlates with a smaller range for the boreal owls there. This strengthens the proposed explanation.

C This option concerns a correlation between owls’ need for food and the frequency with which owls hunt, whereas the phenomenon described in the passage and the proposed explanation have to do with the range over which owls hunt.

D If one were to assume that boreal owls never hunt near a single location for weeks, that would in no way undermine the proposed explanation.

E If anything, this option tends to undermine the proposed explanation, because it suggests the possibility that boreal owls need not make up for the relative scarcity of prey in their habitats by ranging over larger areas.

The correct answer is B.

4.Microbiologist: A lethal strain of salmonella recently showed up in a European country, causing an outbreak of illness that killed two people and infected twenty-seven others. Investigators blame the severity of the outbreak on the overuse of antibiotics, since the salmonella bacteria tested were shown to be drug-resistant. But this is unlikely because patients in the country where the outbreak occurred cannot obtain antibiotics to treat illness without a prescription, and the country’s doctors prescribe antibiotics less readily than do doctors in any other European country.

Which of the following, if true, would most weaken the microbiologist’s reasoning?(B)

A. Physicians in the country where the outbreak occurred have become hesitant to prescribe antibiotics since they are frequently in short supply.

B. People in the country where the outbreak occurred often consume foods produced from animals that eat antibiotics-laden livestock feed.

C. Use of antibiotics in two countries that neighbor the country where the outbreak occurred has risen over the past decade.

D. Drug-resistant strains of salmonella have not been found in countries in which antibiotics are not generally available.

E. Salmonella has been shown to spread easily along the distribution chains of certain vegetables, such as raw tomatoes.

解析:Argument Evaluation

Situation Antibiotic-resistant salmonella caused an outbreak of illness in a European country where patients need prescriptions to obtain antibiotics and where doctors dispense such prescriptions less readily than in other European countries.

Reasoning What evidence would most strongly suggest that overuse of antibiotics was likely responsible for the outbreak, despite the cited facts? The microbiologist reasons that because patients need prescriptions to obtain antibiotics in the country where the outbreak occurred, and the country’s doctors dispense such prescriptions less readily than doctors in other European countries do, antibiotics are probably not being overused in the country—so antibiotic overuse was probably not responsible for the outbreak. Implicit in the microbiologist s reasoning is the assumption that overuse of antibiotics, if it had occurred, could probably have resulted only from overprescribing of antibiotics by physicians to treat illness in people in the country in question. Any evidence casting doubt on this complex assumption would suggest a weakness in the microbiologist’s reasoning.

A This strengthens the argument by providing additional evidence that antibiotics are not being overprescribed in the country.

B Correct. This weakens the microbiologist’s argument by indicating that an assumption implicit in the argument may be false: the salmonella outbreak could easily by explained by overuse of antibiotics in livestock feed (perhaps imported from other countries).

C Even if antibiotic use has risen in the two neighboring countries, antibiotics still might be underused in both countries.

D This suggests that antibiotic-resistant salmonella arises only in countries where antibiotics are used; even if this were true it would be quite compatible with the microbiologist’s argument and does not weaken that argument.

E This describes one mechanism by which salmonella can spread in a population; it says nothing about whether an outbreak of antibiotic-resistant strains of salmonella might have been caused by antibiotic overuse.

The correct answer is B.

5.Historian: Newton developed mathematical concepts and techniques that are fundamental to modern calculus. Leibniz developed closely analogous concepts and techniques. It has traditionally been thought that these discoveries were independent. Researchers have, however, recently discovered notes of Leibniz’s that discuss one of Newton’s books on mathematics. Several scholars have argued that since the book includes a presentation of Newton’s calculus concepts and techniques, and since the notes were written before Leibniz’s own development of calculus concepts and techniques, it is virtually certain that the traditional view is false. A more cautious conclusion than this is called for, however. Leibniz’s notes are limited to early sections of Newton’s book, sections that precede the ones in which Newton’s calculus concepts and techniques are presented.

In the historian’s reasoning, the two portions in boldface play which of the following roles?(B)

A. The first is a claim that the historian rejects; the second is a position that that claim has been used to support.

B. The first is evidence that has been used to support a conclusion about which the historian expresses reservations; the second is that conclusion.

C. The first provides evidence in support of a position that the historian defends; the second is that position.

D. The first and the second each provide evidence in support of a position that the historian defends.

E. The first has been used in support of a position that the historian rejects; the second is a conclusion that the historian draws from that position.

解析:Argument Construction

Situation A historian discusses a controversy about whether or not Leibniz developed calculus concepts and techniques independently of Newton.

Reasoning What argumentative roles do the two portions in boldface play in the passage? The first four sentences of the passage simply provide background information. Both boldface sections are within the fifth sentence, which reports an argument by several scholars. The key word since indicates that the first boldface section is a premise in the scholars’ argument. A second premise preceded by another since follows in the next clause. The final clause of the fifth sentence reveals that the second boldface section is the conclusion of the scholars’ argument. In the sixth sentence, the historian expresses misgivings about the scholars’ conclusion, for reasons presented in the seventh and final sentence.

A The historian does not reject the claim that Newton’s book includes a presentation of Newton’s calculus concepts and techniques. Instead, the historian merely points out that Leibniz’s notes do not cover those sections of Newton’s book.

B Correct. The first boldface section is one of two premises in the scholars’ argument, and the second boldface section is that argument’s conclusion. In the following sentence the historian expresses reservations about that conclusion.

C The historian does not defend the scholars’ conclusion but rather expresses misgivings about it.

D The second boldface section is the scholars’ conclusion and does not present any evidence. Nor does it support the historian’s position that a more cautious conclusion is called for.

E The second boldface section presents not the historian’s conclusion but rather the scholars’ conclusion, about which the historian expresses misgivings.

The correct answer is B.

6.For over two centuries, no one had been able to make Damascus blades—blades with a distinctive serpentine surface pattern—but a contemporary sword maker may just have rediscovered how. Using iron with trace impurities that precisely matched those present in the iron used in historic Damascus blades, this contemporary sword maker seems to have finally hit on an intricate process by which he can produce a blade indistinguishable from a true Damascus blade.

Which of the following, if true, provides the strongest support for the hypothesis that trace impurities in the iron are essential for the production of Damascus blades?(D)

A. There are surface features of every Damascus blade—including the blades produced by the contemporary sword maker—that are unique to that blade.

B. The iron with which the contemporary sword maker made Damascus blades came from a source of iron that was unknown two centuries ago.

C. Almost all the tools used by the contemporary sword maker were updated versions of tools that were used by sword makers over two centuries ago.

D. Production of Damascus blades by sword makers of the past ceased abruptly after those sword makers’ original source of iron became exhausted.

E. Although Damascus blades were renowned for maintaining a sharp edge, the blade made by the contemporary sword maker suggests that they may have maintained their edge less well than blades made using what is now the standard process for making blades.

解析:Argument Evaluation

Situation A sword maker may have recently rediscovered how to make Damascus blades using iron with trace impurities matching those in the iron from which historic Damascus blades were wrough .

Reasoning What evidence would suggest that the trace impurities are essential for producing Damascus blades? The passage says the sword maker seems to have created blades indistinguishable from historic Damascus blades by using iron with the same trace impurities found in those blades. But that does not prove the trace impurities are essential to the process. Evidence suggesting that Damascus blades have never been made from iron without the trace impurities would support the hypothesis that the trace impurities are essential to their manufacture.

A Damascus blades could vary in their surface features whether or not trace impurities are essential for their manufacture.

B Whatever the source of the iron the contemporary sword maker used, it contains the same trace impurities as the iron historically used to make Damascus blades, which is what the hypothesis is about.

C If anything, this might cast doubt on the hypothesis by suggesting that the special tools rather than the trace impurities could account for the distinctive features of Damascus blades.

D Correct. This suggests that when the historic sword makers lost access to the special iron with its trace impurities, they could no longer make Damascus blades. Thus, it supports the hypothesis that the trace impurities are necessary for manufacturing Damascus blades.

E Even if Damascus blades maintained their edges less well than most contemporary blades do, the trace impurities may not have been essential for manufacturing them.

The correct answer is D.

7.Images from ground-based telescopes are invariably distorted by the Earth’s atmosphere. Orbiting space telescopes, however, operating above Earth’s atmosphere, should provide superbly detailed images. Therefore, ground-based telescopes will soon become obsolete for advanced astronomical research purposes.

Which of the following statements, if true, would cast the most doubt on the conclusion drawn above?(E)

A. An orbiting space telescope due to be launched this year is far behind schedule and over budget, whereas the largest ground-based telescope was both within budget and on schedule.

B. Ground-based telescopes located on mountain summits are not subject to the kinds of atmospheric distortion which, at low altitudes, make stars appear to twinkle.

C. By careful choice of observatory location, it is possible for large-aperture telescopes to avoid most of the kind of wind turbulence that can distort image quality.

D. When large-aperture telescopes are located at high altitudes near the equator, they permit the best Earth-based observations of the center of the Milky Way Galaxy, a prime target of astronomical research.

E. Detailed spectral analyses, upon which astronomers rely for determining the chemical composition and evolutionary history of stars, require telescopes with more light-gathering capacity than space telescopes can provide.

解析:Argument Evaluation

Situation Earth’s atmosphere distorts images from ground-based telescopes, whereas space telescopes orbiting above the atmosphere should provide superbly detailed images.

Reasoning What evidence would undermine the claim that ground-based telescopes will soon become obsolete for advanced astronomical research? The argument implicitly assumes that advanced astronomical research can be accomplished more effectively with the more detailed, less distorted images produced by space telescopes and that therefore almost all advanced astronomical research will soon be conducted with space telescopes. This reasoning would be undermined by evidence that ground-based telescopes have substantial advantages for advanced astronomical research despite their distorted images or by evidence that space telescopes will not soon become common or affordable enough to support most advanced astronomical research.

A Even if this is true, there may be several orbiting space telescopes that will be, or have been, launched on schedule and within budget, so this option does not cast doubt on the conclusion of the argument.

B Ground-based telescopes on mountain summits are still subject to more atmospheric distortion than are space telescopes orbiting above the atmosphere.

C Atmospheric distortion of telescopic images may result mainly from factors other than wind turbulence.

D Even the best Earth-based observations of the center of the Milky Way Galaxy may be vastly inferior to space-based observations.

E Correct. This indicates an inherent limitation of space-based telescopes: unlike Earth-based telescopes, they lack the light-gathering capacity that astronomers need to perform one of their primary tasks, i.e., detailed spectral analyses. So Earth-based telescopes are unlikely to soon become obsolete.

The correct answer is E.

8.Generally scientists enter their field with the goal of doing important new research and accept as their colleagues those with similar motivation. Therefore, when any scientist wins renown as an expounder of science to general audiences, most other scientists conclude that this popularizer should no longer be regarded as a true colleague.

The explanation offered above for the low esteem in which scientific popularizers are held by research scientists assumes that(D)

A. serious scientific research is not a solitary activity, but relies on active cooperation among a group of colleagues

B. research scientists tend not to regard as colleagues those scientists whose renown they envy

C. a scientist can become a famous popularizer without having completed any important research

D. research scientists believe that those who are well known as popularizers of science are not motivated to do important new research

E. no important new research can be accessible to or accurately assessed by those who are not themselves scientists

解析:Argument Construction

Situation Research scientists desire to do important new research and treat as colleagues just those who have a similar desire. When a scientist becomes popular among a general audience for explaining principles of science, other scientists have less esteem for this popularizer, no longer regarding such a scientist as a serious colleague.

Reasoning What assumption do research scientists make about scientists who become popularizers? The community of scientists shares a common goal: to do important new research. What would cause this community to disapprove of a popularizer and to cease to regard the popularizer as a colleague ? It must be because many scientists believe that becoming a popularizer is incompatible with desining to do important new research.

A Many scientists make this assumption, of course—but it is not an assumption on which the explanation specifically depends. The explanation concerns the scientists’ motivation, not their style of doing research.

B This statement gives another reason that scientists may reject a popularizer, but because it is not the reason implied in the passage, it is not assumed.

C Even if this is true, it does not address the core issue of the argument: what scientists believe about the motivation of popularizers.

D Correct. This statement properly identifies an assumption on which the explanation for scientists’ rejet tion of popularizers depends.

E The passage is not concerned with whether nonscientists can understand new research, but rather with the beliefs and motivations of scientists who reject popularizers as colleagues.

The correct answer is D.

9.Urban planner: When a city loses population due to migration, property taxes in that city tend to rise. This is because there are then fewer residents paying to maintain an infrastructure that was designed to support more people. Rising property taxes, in turn, drive more residents away, compounding the problem. Since the city of Stonebridge is starting to lose population, the city government should therefore refrain from raising property taxes.

Which of the following, if true, would most weaken the urban planner’s argument?(A)

A. If Stonebridge does not raise taxes on its residents to maintain its infrastructure, the city will become much less attractive to live in as that infrastructure decays.

B. Stonebridge at present benefits from grants provided by the national government to help maintain certain parts of its infrastructure.

C. If there is a small increase in property taxes in Stonebridge and a slightly larger proportion of total revenue than at present is allocated to infrastructure maintenance, the funding will be adequate for that purpose.

D. Demographers project that the population of a region that includes Stonebridge will start to increase substantially within the next several years.

E. The property taxes in Stonebridge are significantly lower than those in many larger cities.

解析:Argument Evaluation

Situation When a city loses population due to migration, fewer residents remain to pay to maintain the city’s infrastructure, so property taxes tend to rise. These rising property taxes then drive even more residents away. The city of Stonebridge is starting to lose population, so Stonebridge’s government should not raise property taxes.

Reasoning What would weaken the urban planner’s justification for concluding that Stonebridge’s government should refrain from raising property taxes? The urban planner implicitly reasons that raising property taxes in Stonebridge in order to maintain the city’s infrastructure would make the city lose even more residents, leaving even fewer paying to maintain the infrastructure, and that this would worsen the funding problem the tax increase would have been intended to solve. The urban planner’s argument would be weakened by any evidence that raising property taxes in Stonebridge would not drive residents away or that refraining from raising property taxes would cause the same problems as raising them would cause, or worse.

A Correct. This suggests that refraining from raising property taxes could drive more residents out of Stonebridge than raising them would, and thus would not help the city avoid the problem the urban planner describes.

B This does slightly weaken the argument because the grants may still be provided to maintain certain parts of the infrastructure, even if increased property taxes drive more residents away. But losing more residents could still make it harder to raise enough funds to maintain the rest of the city’s infrastructure, as the urban planner argues.

C Even if this approach would address the immediate maintenance funding problem, the small increase in property taxes could still drive more residents away, forcing additional future tax increases on those who remain, just as the urban planner suggests.

D This does slightly weaken the argument, but the residents who will move to the region might still avoid moving to Stonebridge if the property taxes there are too high, and those who live in Stonebridge might still move to other cities in the region. E Residents fleeing Stonebridge because of high property taxes would likely avoid moving to the many larger cities with even higher property taxes, but they might be happy to move to many other places with low property taxes.

The correct answer is A.

10.Which of the following most logically completes the argument?

Utrania was formerly a major petroleum exporter, but in recent decades economic stagnation and restrictive regulation . inhibited investment in new oil fields. In consequence, Utranian oil exports dropped steadily as old fields became depleted. Utrania’s currently improving economic situation, together with less-restrictive regulations, will undoubtedly result in the rapid development of new fields. However, it would be premature to conclude that the rapid development of new fields will result in higher oil exports, because_________.(B)

A. the price of oil is expected to remain relatively stable over the next several years

B. the improvement in the economic situation in Utrania is expected to result in a dramatic increase in the proportion of Utranians who own automobiles

C. most of the investment in new oil fields in Utrania is expected to come from foreign sources

D. new technology is available to recover oil from old oil fields formerly regarded as depleted

E. many of the new oil fields in Utrania are likely to be as productive as those that were developed during the period when Utrania was a major oil exporter

解析:Argument Construction

Situation A country that had been a major oil exporter has seen its exports decline in recent decades dut to economic stagnation, a failure to invest in new fields, and the steady depletion of its old fields. But looser regulations and an improving economy will bring rapid development of new oil fields ir the country.

Reasoning Which of the options would most logically complete the argument? The passage describes the condit ons that led to Utrania’s no longer being a major oil exporter: a lack of investment in new oil fields due to a stagnant economy and restrictive regulations. The passage then says that due to changed regulatory and economic conditions, there will now be rapid development of new oil fields. Nonetheless, this might not bring about an increase in Utrania’s oil exports. To logically complete the argument, one must explain how oil exports might not increase even when the condition that led to decreased oil exports has been removed. Suppose there were an increase in domestic oil consumption. A dramatic increase in the rate of car ownership in Utrania could reasonably be expected to significantly increase domestic oil consumption, which could eat up the added oil production from the new fields.

A This choice is incorrect. There is no reason why stable oil prices should prevent Utrania’s oil exports from increasing.

B Correct. An increase in car ownership would increase Utrania’s oil consumption—and this supports the claim that oil exports might not increase.

C If anything, this suggests that oil exports should increase. So it would not be a good choice for completion of the argument.

D The advent of new technology allowing oil to be extracted from fields previously thought to be depleted would mean that there is even more reason to think that Utrania’s oil exports will increase.

E This does not help to explain why exports would not increase. On the contrary, it suggests that the new fields will lead to increased exports.

The correct answer is B.

11.The use of growth-promoting antibiotics in hog farming can weaken their effectiveness in treating humans because such use can spread resistance to those antibiotics among microorganisms. But now the Smee Company, one of the largest pork marketers, may stop buying pork raised on feed containing these antibiotics. Smee has 60 percent of the pork market, and farmers who sell to Smee would certainly stop using antibiotics in order to avoid jeopardizing their sales. So if Smee makes this change, it will probably significantly slow the decline in antibiotics’ effectiveness for humans.

Which of the following, if true, would most strengthen the argument above?(A)

A. Other major pork marketers will probably stop buying pork raised on feed containing growth-promoting antibiotics if Smee no longer buys such pork.

B. The decline in hog growth due to discontinuation of antibiotics can be offset by improved hygiene.

C. Authorities are promoting the use of antibiotics to which microorganisms have not yet developed resistance.

D. A phaseout of use of antibiotics for hogs in one country reduced usage by over 50 percent over five years.

E. If Smee stops buying pork raised with antibiotics, the firm’s costs will probably increase.

解析:Argument Evaluation

Situation Using growth-promoting antibiotics in hog farming can produce widespread resistance to antibiotics among microorganisms, thereby making the antibiotics less effective in treating humans. The Smee Company, a pork marketer with 60 percent of the pork market, may stop buying pork raised on feed containing these antibiotics.

Reasoning What additional evidence would most help to support the conclusion that if Smee makes the change, it will significantly slow the decline in antibiotics’ effectiveness for humans? We are already informed that if Smee makes the change, it will eliminate the use of antibiotics in hog feed by farmers supplying at least 60 percent of the pork market. The argument would be strengthened by evidence that Smee’s decision would indirectly cause use of the antibiotics to stop more broadly, for example in hog farms supplying significantly more than 60 percent of the total amount of pork marketed.

A Correct. This suggests that if Smee makes the change, hog farmers supplying other major pork marketers will also have to stop using antibiotics in hog feed, making the change more widespread and thus probably more effective.

B Even if the decline in hog growth from discontinuing the antibiotics cannot be offset, many hog farmers will still have to stop using the antibiotics as a result of Smee’s decision. On the other hand, even if the decline can be offset with improved hygiene, that change might be too expensive or difficult to be worth its benefits for most hog farmers.

C Whatever new antibiotics authorities are promoting, microorganisms may soon develop resistance to them as well. Smee may or may not refuse to buy pork raised on feed containing these new antibiotics.

D This is evidence that Smee’s decision may significantly reduce antibiotic use in hogs, but it provides no evidence of how this reduction may affect antibiotics’effectiveness for humans.

E If anything, this provides reason to suspect that Smee will not stick with the change for long after the costs increase, so it weakens rather than strengthens the argument that the change will significantly slow the decline in antibiotics’ effectiveness.

The correct answer is A.

12.In an experiment, volunteers walked individually through a dark, abandoned theater. Half of the volunteers had been told that the theater was haunted and the other half that it was under renovation. The first half reported significantly more unusual experiences than the second did. The researchers concluded that reports of encounters with ghosts and other supernaural entities generally result from prior expectations of such experiences.

Which of the following, if true, would most seriously weaken the researchers’ reasoning?(B)

A. None of the volunteers in the second half believed that the unusual experiences they reported were supernatural.

B. All of the volunteers in the first half believed that the researchers’ statement that the theater was haunted was a lie.

C. Before being told about the theater, the volunteers within each group varied considerably in their prior beliefs aboujt supernatural experiences.

D. Each unusual experience reported by the volunteers had a cause that did not involve the supernatural.

E. The researchers did not believe that the theater was haunted.

解析:Argument Evaluation

Situation Volunteers in an experiment walked through a dark, abandoned theater. Those who had been told the theater was haunted reported more unusual experiences than those who had been told it was under renovation.

Reasoning What evidence would most strongly suggest that the experimental results do not indicate that reports of supernatural encounters result from prior expectations of such experiences? The researcher assumes that the half of the volunteers who had been told the theater was haunted were more inclined to expect supernatural experiences in the theater than were the other half of the volunteers. Based on this assumption and the greater incidence of reports of unusual experiences among the first half of the volunteers, the researcher concludes that prior expectation of supernatural experiences makes people more likely to report such experiences. The researchers’ reasoning would be weakened by evidence that the volunteers did not actually have the expectations the researchers assumed them to have, or by evidence that any such expectations did not influence their reports.

A This strengthens the argument by indicating that the volunteers whom the researchers did not lead to expect supernatural experiences reported no such experiences.

B Correct. If none of the volunteers believed the researchers’ claim that the theater was haunted, then the implicit assumption that several of those volunteers expected supernatural experiences in the theater is flawed, and so the inference that their prior expectations probably account for their reports of supernatural experiences is flawed.

C This is compatible with the researchers’ inference and does not undermine it. Even if the volunteers’ initial beliefs about supernatural experiences varied, the researchers’ claims about the theater might have strongly influenced how many volunteers in each group expected to have such experiences in the theater specifically.

D The researchers argue that the volunteers’ prior expectations account for all the reports of unusual experiences, and this is compatible with there being no genuine supernatural occurrences in the theater.

E Whatever the researchers personally believed about the theater, they might still have successfully influenced the volunteers’ beliefs about it.

The correct answer is B.

13.In order to reduce dependence on imported oil, the government of Jalica has imposed minimum fuel-efficiency requirements on all new cars, beginning this year. The more fuel-efficient a car, the less pollution it produces per mile driven. As Jalicans replace their old cars with cars that meet the new requirements, annual pollution from car traffic is likely to decrease in Jalica.

Which of the following, if true, most seriously weakens the argument?(E)

A. In Jalica, domestically produced oil is more expensive than imported oil.

B. The Jalican government did not intend the new fuel-efficiency requirement to be a pollution-reduction measure.

C. Some pollution-control devices mandated in Jalica make cars less fuel-efficient than they would be without those devices.

D. The new regulation requires no change in the chemical formulation of fuel for cars in Jalica.

E. Jalicans who get cars that are more fuel-efficient tend to do more driving than before.

解析:Argument Evaluation

Situation The Jalican government is requiring all new cars to meet minimum fuel-efficiency requirements starting this year. Cars that are more fuel efficient produce less pollution per mile driven.

Reasoning What evidence would suggest that annual pollution from car traffic will not decrease in Jalica, despite the new policy? Air pollution from car traffic is unlikely to decrease if the new standards will result in more cars on the road or more miles driven per car; or if air pollution from car traffic in Jalica is increasing because of unrelated factors such as growing numbers of Jalicans who can afford cars, construction of more roads, etc. Evidence that any of these factors is present would cast doubt on the argument’s conclusion and thus weaken the argument.

A The question at issue is not whether the new policy will reduce dependence on imported oil as the government intends, but rather whether it will reduce air pollution from car traffic.

B A government policy may have consequences that the government did not intend it to have.

C Even if these pollution-control devices make cars less fuel efficient, the new fuel-efficiency standards may still improve cars’ average fuel efficiency and thereby reduce air pollution.

D Even if the fuel is unchanged, the new fuel-efficiency standards may still result in cars using less fuel and may thereby reduce air pollution.

E Correct. If the new fuel-efficient cars are driven more miles per year than older cars are, they may produce as much or more pollution per year than older cars do even though they produce less pollution per mile driven.

The correct answer is E.

14.Plantings of cotton bioengineered to produce its own insecticide against bollworms, a major cause of crop failure, sustained little bollworm damage until this year. This year the plantings are being seriously damaged by bollworms. Bollworms, however, are not necessarily developing resistance to the cotton’s insecticide. Bollworms breed on corn, and last year more corn than usual was planted throughout cotton-growing regions. So it is likely that the cotton is simply being overwhelmed by corn-bred bollworms.

In evaluating the argument, which of the following would it be most useful to establish?(B)

A. Whether corn could be bioengineered to produce the insecticide

B. Whether plantings of cotton that does not produce the insecticide are suffering unusually extensive damage from bollworms this year

C. Whether other crops that have been bioengineered to produce their own insecticide successfully resist the pests against which the insecticide was to protect them

D. Whether plantings of bioengineered cotton are frequently damaged by insect pests other than bollworms

E. Whether there are insecticides that can be used against bollworms that have developed resistance to the insecticide produced by the bioengineered cotton

解析:Argument Evaluation

Situation Although plantings of cotton bioengineered to produce an insecticide to combat bollworms were little damaged by the pests in previous years, they are being severely damaged this year. Since the bollworms breed on corn, and there has been more corn planted this year in cotton-growing areas, the cotton is probably being overwhelmed by the corn-bred bollworms.

Reasoning In evaluating the argument, which question would it be most useful to have answered? The argument states that the bioengineered cotton crop failures this year (1) have likely been due to the increased corn plantings and (2) not due to the pests having developed a resistance to the insecticide. This also implies (3) that the failures are not due to some third factor.

It would be useful to know how the bioengineered cotton is faring in comparison to the rest of this year’s cotton crop. If the bioengineered cotton is faring better against the bollworms, that fact would support the argument because it would suggest that the insecticide is still combating bollworms If, on the other hand, the bioengineered cotton is being more severely ravaged by bollworms than is other cotton, that suggests that there is some third cause that is primarily at fault.

A This would probably be useful information to those trying to alleviate the bollworm problem in

bioengineered cotton. But whether such corn could be developed has no bearing on what is causing the bioengineered cotton to be damaged by bollworms this year.

B Correct. If bollworm damage on non-bioengineered cotton is worse than usual this year, then bollworm infestation in general is simply worse than usual, so pesticide resistance does not need to be invoked to explain the bollworm attacks on the bioengineered cotton.

C Even if other crops that have been bioengineered to resist pests have not successfully resisted them, that fact would not mean that the same is true of this cotton. Furthermore, the facts already suggest that the bioengineered cotton has resisted bollworms.

D Whether other types of pests often damage bioengineered cotton has no bearing on why bollworms are damaging this type of cotton more this year than in the past.

E This, too, might be useful information to those trying to alleviate the bollworm problem in bioengineered cotton, but it is not particularly useful in evaluating the argument. Even if there are pesticides that could be used against bollworms that have developed resistance to the insecticide of the bioengineered cotton, that does not mean that such pesticides are being used this year.

The correct answer is B.

15.Typically during thunderstorms most lightning strikes carry a negative electric charge; only a few carry a positive charge. Thunderstorms with unusually high proportions of positive-charge strikes tend to occur in smoky areas near forest fires. The fact that smoke carries positively charged smoke particles into the air above a fire suggests the hypothesis that the extra positive strikes occur because of the presence of such particles in the storm clouds.

Which of the following, if discovered to be true, most seriously undermines the hypothesis?(D)

A. Other kinds of rare lightning also occur with unusually high frequency in the vicinity of forest fires.

B. The positive-charge strikes that occur near forest fires tend to be no more powerful than positive strikes normally are.

C. A positive-charge strike is as likely to start a forest fire as a negative-charge strike is.

D. Thunderstorms that occur in drifting clouds of smoke have extra positive-charge strikes weeks after the charge of the smoke particles has dissipated.

E. The total number of lightning strikes during a thunderstorm is usually within the normal range in the vicinity of a forest fire.

解析:Argument Evaluation

Situation Thunderstorms with unusually high proportions of positive-charge lightning strikes tend to occur in smoky areas near forest fires. Smoke carries positively charged particles into the air above fires, suggesting that smoke particles in storm clouds are responsible for the higher proportion of positive strikes.

Reasoning What would cast doubt on the hypothesis that the extra positive-charge lightning strikes in thunderstorms near forest fires result from positively charged smoke particles carried into the storm clouds? The hypothesis would be weakened by evidence that the positively charged smoke particles do not enter the storm clouds in the first place, or that they do not retain their charge in the clouds long enough to produce an effect, or that their positive charge cannot affect the charges of the storm’s lightning strikes in any case, or that some other factor tends to make the lightning strikes above these storms positively charged.

A It could be that positively charged smoke particles cause these other kinds of rare lightning, too, so this does not seriously undermine the hypothesis.

B The hypothesis is not about the power of the positive-charge lightning strikes, only about why a high proportion of them occur in thunderstorms near forest fires.

C The hypothesis is about why positive-charge strikes tend to occur in smoky areas near forest fires that have already started before the strikes occur. Furthermore, an equal likelihood of positive-charge and negative-charge strikes starting fires cannot explain a correlation between fires and positive-charge strikes specifically.

D Correct. This means that even when drifting clouds of smoke persist for weeks after a fire, when the charge of their particles has already dissipated, the smoke somehow still makes the strikes positively charged in any thunderstorms arising within it. If so, some factor other than positively charged smoke particles must affect the strikes’ charge.

E This information does not undermine the hypothesis. The hypothesis does not concern the possibility that there might be more lightning strikes in the vicinity of forest fires; rather it concerns the proportion of all such lightning strikes that are positively charged.

The correct answer is D.

16.Many gardeners believe that the variety of clematis vine that is most popular among gardeners in North America is jackmanii. This belief is apparently correct since, of the one million clematis plants sold per year by the largest clematis nursery in North America, ten percent are jackmanii.

Which of the following is an assumption on which the argument depends?(A)

A. The nursery sells more than ten different varieties of clematis.

B. The largest clematis nursery in North America sells nothing but clematis plants.

C. Some of the jackmanii sold by the nursery are sold to gardeners outside North America.

D. Most North American gardeners grow clematis in their gardens.

E. For all nurseries in North America that specialize in clematis, at least ten percent of the clematis plants they sell are jackmanii.

解析:Argument Construction

Situation Of the clematis plants sold by the largest clematis nursery in North America, 10 percent are jackmanii, which many gardeners believe to be the most popular variety of clematis in North America.

Reasoning What must be true in order for the fact that 10 percent of the clematis sold at the nursery are jackmanii to provide evidence that jackmanii is the most popular variety of clematis in North America? The argument assumes that sales of different varieties of clematis at the nursery reflect the relative levels of popularity of those varieties among North American gardeners. It also assumes that jackmanii is the best-selling clematis variety at the nursery, an assumption which requires that ess than 10 percent of the nursery’s clematis sales are of any one variety other than jackmanii.

A Correct. Suppose the nursery sold ten or fewer varieties of clematis. Then at least one variety other than jackmanii would have to account for at least 10 percent of the nursery’s clematis sales, so jackmanii would not be the best-selling clematis variety at the nursery as the argument assumes.

B The argument only concerns how popular jackmanii is relative to other varieties of clematis, not relative to any plants other than clematis that the nursery may sell.

C If anything, this would weaken the argument by suggesting that the nursery’s jackmanii sales might refect jackmanii’s popularity outside North America more than its popularity within North America.

D This would indicate that clematis is a popular plant among North American gardeners, not that jackmanii is the most popular variety of clematis.

E Even if jackmanii accounts for less than 10 percent of clematis sales at a few individual nurseries, it may still account for 10 percent or more of North American clematis sales overall.

The correct answer is A.

17.Since 1990 the percentage of bacterial sinus infections in Aqadestan that are resistant to the antibiotic perxicillin has increased substantially. Bacteria can quickly develop resistance to an antibiotic when it is prescribed indiscriminately or when patients fail to take it as prescribed. Since perxicillin has not been indiscriminately prescribed, health officials hypothesize that the increase in perxicillin-resistant sinus infections is largely due to patients’ failure to take this medication as prescribed.

Which of the following, if true of Aqadestan, provides most support for the health officials’ hypothesis?(D)

A. Resistance to several other commonly prescribed antibiotics has not increased since 1990 in Aqadestan.

B. A large number of Aqadestanis never seek medical help when they have a sinus infection.

C. When it first became available, perxicillin was much more effective in treating bacterial sinus infections than any other antibiotic used for such infections at the time.

D. Many patients who take perxicillin experience severe side effects within the first few days of their prescribed regimen.

E. Aqadestani health clinics provide antibiotics to their patients at cost.

解析:Argument Construction

Situation In Aqadestan the percentage of bacterial sinus infections resistant to the antibiotic perxicillin has been increasing even though perxicillin has not been indiscriminately prescribed.

Reasoning What evidence most strongly suggests that the main reason perxicillin-resistant sinus infections are becoming more common is that patients are failing to take perxicillin as prescribed? Any evidence suggesting that patients have in fact been failing to take perxicillin as prescribed would support the hypothesis, as would any evidence casting doubt on other possible explanations for the increasing proportion of perxicillin-resistant sinus infections.

A This suggests that some factor specific to perxicillin is increasing bacterial resistance to it, but that could be true whether or not the factor is patients’ failure to take perxicillin as prescribed.

B If anything, this weakens the argument by suggesting that most people with sinus infections are never prescribed perxicillin, and that therefore relatively few people are getting prescriptions and then failing to follow them.

C The relative effectiveness of perxicillin when it first became available does not suggest that the reason it is now becoming less effective is that many patients are failing to take it as prescribed.

D Correct. These side effects would discourage patients from taking perxicillin as prescribed, so their existence provides evidence that many patients are not taking it as prescribed.

E If the clinics do not charge extra for perxicillin, that would make it more affordable and hence easier for many patients to take as prescribed.

The correct answer is D.

18.Psychologist: In a study, researchers gave 100 volunteers a psychological questionnaire designed to measure their self esteem. The researchers then asked each volunteer to rate the strength of his or her own social skills. The volunteers with the highest levels of self-esteem consistently rated themselves as having much better social skills than did the volunteers with moderate levels. This suggests that attaining an exceptionally high level of self-esteem greatly improves one’s social skills.

The psychologist’s argument is most vulnerable to criticism on which of the following grounds?(C)

A. It fails to adequately address the possibility that many of the volunteers may not have understood what the psychological questionnaire was designed to measure.

B. It takes for granted that the volunteers with the highest levels of self-esteem had better social skills than did the other volunteers, even before the former volunteers had attained their high levels of self-esteem.

C. It overlooks the possibility that people with very high levels of self-esteem may tend to have a less accurate perception of the strength of their own social skills than do people with moderate levels of self-esteem.

D. It relies on evidence from a group of volunteers that is too small to provide any support for any inferences regarding people in general.

E. It overlooks the possibility that factors other than level of self-esteem may be of much greater importance in determining the strength of one’s social skills.

解析:Argument Evaluation

Situation In a psychological study of 100 volunteers, those found to have the highest self-esteem consistently rated themselves as having much better social skills than did those found to have moderate self-esteem.

Reasoning What is wrong with the psychologist citing the study’s results to justify the conclusion that exceptionally high self-esteem greatly improves social skills? The psychologist reasons that the study shows a correlation between very high self-esteem and how highly one rates one’s social skills, and that this correlation in turn suggests that very high self-esteem improves social skills. This argument is vulnerable to at least two criticisms: First, the argument assumes that the volunteers’ ratings of their own social skills are generally accurate. But very high self-esteem might in many cases result from a tendency to overestimate oneself and one’s skills, including one’s social skills. Second, the argument fails to address the possibility that good social skills promote high self-esteem rather than vice versa, as well as the possibility that some third factor (such as a sunny disposition or fortunate circumstances) promotes both high self-esteem and good social skills.

A An experiment’s subjects do not have to understand the experiment’s design in order for the experimental results to be accurate.

B To the contrary, the argument concludes that the volunteers with the highest self-esteem attained their enhanced social skills as a result of attaining such high self-esteem.

C Correct. As explained above, very high self-esteem may often result from a tendency to overestimate oneself in general, and thus to overestimate one’s social skills.

D A group of 100 volunteers is large enough for an experiment to provide at least a little support for at least some inferences regarding people in general.

E As explained above, the argument overlooks the possibility that some third factor may play a significant role in determining the strength of one’s social skills. But even if some factor other than self-esteem is more important in determining the strength of social skills, that would still be compatible with very high self-esteem being of some importance in improving one’s social skills.

The correct answer is C.

19.A product that represents a clear technological advance over competing products can generally command a high price. Because technological advances tend to be quickly surpassed and companies want to make large profits while they still can, many companies charge the maximum possible price for such a product. But large profits on the new product will give competitors a strong incentive to quickly match the new product’s capabilities. Consequently, the strategy to maximize overall profit from a new product is to charge less than the greatest possible price.

In the argument above, the two portions in boldface play which of the following roles?(C)

A. The first is a consideration raised to argue that a certain strategy is counterproductive; the second presents that strategy.

B. The first is a consideration raised to support the strategy that the argument recommends; the second presents that strategy.

C. The first is a consideration raised to help explain the popularity of a certain strategy; the second presents that strategy.

D. The first is an assumption, rejected by the argument, that has been used to justify a course of action; the second presents that course of action.

E. The first is a consideration that has been used to justify adopting a certain strategy; the second presents the intended outcome of that strategy.

解析:Argument Construction

Situation Often, when a company comes out with an innovative product, it will price the product as high as it can to maximize profits before the competitors quickly catch up. But this is not a good strategy because the very high price of the new product only encourages competitors to match the technological advance more quickly.

Reasoning Which option best describes the roles that the boldface portions play in the argument? This type of item concerns only the argument’s structure—the way it is intended to work, not the quality of the argument or what might strengthen or weaken the argument. So even if a boldface portion could be used by the argument in a certain way, all that matters is its actual intended role. The fact that technological advances tend to be quickly surpassed serves to partly explain why many companies charge the maximum possible price for such a product. In other words, the first boldface portion helps explain the popularity of the strategy presented in the second boldface portion. The conclusion of the argument, however, is that the strategy exemplified in this latter boldface portion is unwise, so the argument as a whole opposes that strategy.

A Although the first boldface portion could be used as part of an argument that the strategy presented in the second boldface portion is counterproductive, that is not how it is used here. Rather, it immediately follows the word because and serves to explain the occurrence of what is described in the second boldface portion.

B This is clearly wrong because the second boldface portion presents the strategy that the argument opposes.

C Correct. It is the only choice that is consistent with the analysis of the reasoning presented above.

D The first boldface portion is not an assumption rejected by the argument; rather, it is affirmed in the argument.

E The argument does not expressly claim that the first boldface portion has been used to justify the strategy of setting the price as high as possible, although it implies that this is part of the justification that those adopting the strategy would give. More clearly, the second boldface portion does not describe the intended outcome of the strategy, but rather the means of bringing about that intended outcome (maximizing profits, by means of high prices).

The correct answer is C.

20.Gortland has long been narrowly self-sufficient in both grain and meat. However, as per capita income in Gortland has risen toward the world average, per capita consumption of meat has also risen toward the world average, and it takes several pounds of grain to produce one pound of meat. Therefore, since per capita income continues to rise, whereas domestic grain production will not increase, Gortland will soon have to import either grain or meat or both.

Which of the following is an assumption on which the argument depends?(E)

A. The total acreage devoted to grain production in Gortland will not decrease substantially.

B. The population of Gortland has remained relatively constant during the country’s years of growing prosperity.

C. The per capita consumption of meat in Gortland is roughly the same across all income levels.

D. In Gortland, neither meat nor grain is subject to government price controls.

E. People in Gortland who increase their consumption of meat will not radically decrease their consumption of grain.

解析:Argument Construction

Situation A country previously self-sufficient in grain and meat will soon have to import one or the other or both because its consumption of meat has risen as per capita income has risen. It takes several pounds of grain to produce one pound of meat.

Reasoning What conditions must be true for the conclusion to be true? Meat consumption is rising. What about grain consumption? A sharp reduction in the amount of grain directly consumed by meat eaters could compensate for increased meat consumption, making the conclusion false. If people did radically decrease their grain consumption, it might not be necessary to import grain or meat. Since the argument concludes that the imports are necessary, it assumes that direct consumption of grain by those who begin to eat meat will not plunge.

A The argument makes no assumptions about the acreage devoted to grain; it assumes only that the demand for grain will rise.

B The argument is based on rising per capita income, not population levels.

C The argument involves only meat consumption in general, not its distribution by income level.

D Since the argument does not refer to price controls, it cannot depend on an assumption about them.

E Correct. This statement properly identifies the assumption that those who begin to eat meat do not then greatly decrease their direct consumption of grains.

The correct answer is E.

21.Political Advertisement:

Mayor Delmont’s critics complain about the jobs that were lost in the city under Delmont’s leadership. Yet the fact is that not only were more jobs created than were eliminated, but each year since Delmont took office the average pay for the new jobs created has been higher than that year’s average pay for jobs citywide. So it stands to reason that throughout Delmont’s tenure the average paycheck in this city has been getting steadily bigger.

Which of the following, if true, most seriously weakens the argument in the advertisement?(C)

A. The unemployment rate in the city is higher today than it was when Mayor Delmont took office.

B. The average pay for jobs in the city was at a ten-year low when Mayor Delmont took office.

C. Each year during Mayor Delmont’s tenure, the average pay for jobs that were eliminated has been higher than the average pay for jobs citywide.

D. Most of the jobs eliminated during Mayor Delmont’s tenure were in declining industries.

E. The average pay for jobs in the city is currently lower than it is for jobs in the suburbs surrounding the city.

解析:Argument Evaluation

Situation Every year since Mayor Delmont took office, average pay for new jobs has exceeded average pay for jobs citywide. So, the average paycheck in the city has been increasing since Delmont took office.

Reasoning Which option, if true, would most seriously weaken the argument? If average pay for new jobs continually exceeds that for jobs generally, new jobs pay better (on average) than old jobs that still exist. But suppose the following occurred. Every year all of the highest paying jobs are eliminated and replaced with somewhat lower-paying jobs that still pay more than the average job. The result would be that every year the average pay for a new job would be greater than that for existing jobs, but the average pay for all jobs would nonetheless decrease. Thus, if every year during the mayor’s tenure the jobs that were eliminated paid better on average than jobs citywide, that would seriously weaken the argument: the conclusion could be false even if the information on which it is based is true.

A The percentage of people in the city who have a job has no direct bearing on whether the average pay for jobs citywide is increasing or decreasing.

B Whether the average pay was low when the mayor took office in comparison to the ten preceding years is immaterial to the comparison addressed in the argument’s conclusion.

C Correct. This information weakens the argument because it opens up the possibility that the jobs eliminated had higher average pay than the jobs created during Mayor Delmont’s tenure. This in turn would mean that the average pay was not increasing during Mayor Delmont’s tenure.

D This, too, has no bearing on the argument, because we have no information about the average pay for jobs in those declining industries.

E This is also irrelevant. No comparison is made (or implied) in the argument between jobs in the city and jobs in the suburbs.

The correct answer is C.

22.To prevent a newly built dam on the Chiff River from blocking the route of fish migrating to breeding grounds upstream, the dam includes a fish pass, a mechanism designed to allow fish through the dam. Before the construction of the dam and fish pass, several thousand fish a day swam upriver during spawning season. But in the first season after the project’s completion, only 300 per day made the journey. Clearly, the fish pass is defective.

Which of the following, if true, most seriously weakens the argument?(C)

A. Fish that have migrated to the upstream breeding grounds do not return down the Chiff River again.

B. On other rivers in the region, the construction of dams with fish passes has led to only small decreases in the number of fish migrating upstream.

C. The construction of the dam stirred up potentially toxic river sediments that were carried downstream.

D. Populations of migratory fish in the Chiff River have been declining slightly over the last 20 years.

E. During spawning season, the dam releases sufficient water for migratory fish below the dam to swim upstream.

解析:Argument Evaluation

Situation A new dam includes a mechanism called a fish pass designed to allow fish to migrate upstream past the dam to their breeding grounds. The number of migrating fish fell from several thousand per day before the dam was built to three hundred per day in the first season after it was built, indicating—according to the argument—that the fish pass is defective.

Reasoning What evidence would suggest that the fish pass is not defective? The argument implicitly reasons that a defective fish pass would make it difficult for the fish to migrate, which would explain why the number of migrating fish fell when the dam was completed. Any evidence suggesting an alternative explanation for the reduced number of migrating fish, such as an environmental change that occurred when the dam was built, would cast doubt on the argument’s reasoning.

A A defective fish pass could prevent most of the fish from migrating upstream regardless of whether those that succeed ever return downstream.

B This would suggest that dams with properly functioning fish passes do not greatly reduce the number of migrating fish, so it would provide further evidence that the fish pass in this particular dam is defective.

C Correct. This suggests that the toxic sediments may have poisoned the fish and reduced their population. A smaller fish population could be sufficient to explain the reduced number offish migrating, which casts doubt on the argument’s assumption that the explanation for their declining numbers involves the fish pass.

D A slight and gradual ongoing decline in migratory fish populations would not explain an abrupt and extreme decline right after the dam was built.

E This supports the argument’s proposed explanation for the declining fish population by ruling out the alternative explanation that the dam does not release enough water for the fish to migrate.

The correct answer is C.

23.Music critic: Fewer and fewer musicians are studying classical music, decreasing the likelihood that those with real aptitude for such music will be performing it. Audiences who hear these performances will not appreciate classical music’s greatness and will thus decamp to other genres. So to maintain classical music’s current meager popularity, we must encourage more young musicians to enter the field.

Which of the following, if true, most weakens the music critic’s reasoning?(C)

A. Musicians who choose to study classical music do so because they believe they have an aptitude for the music.

B. Classical music’s current meager popularity is attributable to the profusion of other genres of music available to listeners.

C. Most people who appreciate classical music come to do so through old recordings rather than live performances.

D. It is possible to enjoy the music in a particular genre even when it is performed by musicians who are not ideally suited for that genre.

E. The continued popularity of a given genre of music depends in part on the audience’s being able to understand why that genre attained its original popularity.

解析:Argument Evaluation

Situation Fewer musicians are studying classical music. This reduces the likelihood that those performing the music will have real aptitude for it, which in turn reduces audience’s appreciation of classical music performances.

Reasoning What evidence would cast the most doubt on the support provided for the conclusion that encouraging more young musicians to study classical music is necessary in order to maintain the genre’s meager popularity? The music critic’s argument is that because fewer talented classical musicians are performing, audiences hearing their performances will fail to appreciate the genre, and thus will abandon it. The critic reasons that to solve this problem, it will be necessary to encourage more young musicians to study classical music so that audiences will eventually be exposed to more talented classical performers and decide the genre is worthwhile after all. The argument would be weakened, for example, by evidence that hearing unremarkable live performances does not really drive many people away from classical music, or that the number of audience members hearing great performances does not depend much on the number of talented performers, or that encouraging young musicians to study classical music is either ineffective or not the only effective way to increase the number of talented classical performers.

A This does not weaken the critic’s reasoning. However much confidence musicians studying classical music have in their own talent, a decline in the total number of classical musicians will probably result in a decline in the number of truly talented classical musicians, just as the critic assumes.

B The critic is only proposing a way to at least maintain classical music’s current meager popularity, which might be accomplished even if the profusion of other genres prevents classical music’s popularity from increasing.

C Correct. This suggests that classical music’s meager popularity could at least be maintained by encouraging people to listen to great old recordings of classical music rather than by increasing the supply of great live performances.

D This does weaken the argument slightly. But even if a few audience members manage to enjoy mediocre classical music performances, they might still be more strongly drawn to other genres with more talented performers.

E Listeners exposed to more impressive live performances of classical music by talented performers would probably better understand why classical music was once popular than would listeners exposed only to mediocre classical performances.

The correct answer is C.

24.Commemorative plaques cast from brass are a characteristic art form of the Benin culture of West Africa. Some scholars, noting that the oldest surviving plaques date to the 1400s, hypothesize that brass-casting techniques were introduced by the Portuguese, who came to Benin in 1485 A.D. But Portuguese records of that expedition mention cast-brass jewelry sent to Benin’s king from neighboring Ife. So it is unlikely that Benin’s knowledge of brass casting derived from the Portuguese.

Which of the following, if true, most strengthens the argument?(B)

A. The Portuguese records do not indicate whether their expedition of 1485 included metalworkers.

B. The Portuguese had no contact with Ife until the 1500s.

C. In the 1400s the Portuguese did not use cast brass for commemorative plaques.

D. As early as 1500 A.D., Benin artists were making brass plaques incorporating depictions of Europeans.

E. Copper, which is required for making brass, can be found throughout Benin territory.

解析:Argument Construction

Situation The oldest surviving cast-brass plaques from the Benin culture date to the 1400s. Records of a Portuguese expedition to Benin in 1485 mention cast-brass jewelry sent to Benin’s king from neighboring Ife.

Reasoning What additional evidence, when combined with the argument’s premises, would most help support the conclusion that Benin’s knowledge of brass casting did not derive from the Portuguese? The argument is that since the expedition records indicate that cast-brass jewelry from Ife was already known in Benin when the Portuguese first came there, Benin’s knowledge of brass casting probably did not derive from the Portuguese. This argument assumes that receiving the brass-cast jewelry from Ife could have transmitted knowledge of brass casting to Benin, and also that knowledge of brass casting in Ife did not itself derive from the Portuguese. Any evidence supporting either of these assumptions would strengthen the argument.

A This is compatible with a Portuguese origin for brass-casting in Benin. The expedition might well have included metalworkers even if the records do not mention whether it did. Furthermore, other Portuguese expeditions with metalworkers might have quickly followed the initial expedition.

B Correct. If the Portuguese had no contact with Ife before 1500, then Ife’s earlier knowledge of brass casting did not derive directly from the Portuguese. This increases the likelihood that knowledge of brass casting in Benin did not derive from the Portuguese, even if it derived from Ife.

C This is compatible with a Portuguese origin for brass-casting in Benin. Even if the Portuguese did not use cast brass for commemorative plaques, they could have used it for jewelry or other items they brought to Benin or manufactured there, and thus they could have transmitted the knowledge to the Benin culture.

D This leaves open the possibility that the Benin culture learned about brass casting from the Portuguese in 1485 and started using it to produce plaques of this type by 1500.

E Even if copper has always been common in the Benin territory, brass-casting techniques could have been introduced by the Portuguese.

The correct answer is B.

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