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96. Prominent business executives often play active roles in United States presidential campaigns as fundraisers or backroom strategists, but few actually seek to become president themselves. Throughout history the great majority of those who have sought to become president have been lawyers, military leaders, or full-time politicians. This is understandable, for the personality and skills that make for success in business do not make for success in politics. Business is largely hierarchical, whereas politics is coordinative. As a result, business executives tend to be uncomfortable with compromises and power-sharing, which are inherent in politics.

Which one of the following, if true, most seriously weakens the proposed explanation of why business executives do not run for president?

A. Many of the most active presidential fundraisers and backroom strategists are themselves politicians.
B. Military leaders are generally no more comfortable with compromises and power-sharing than are business executives.
C. Some of the skills needed to become a successful lawyer are different from some of those needed to become a successful military leader.
D. Some former presidents have engaged in business ventures after leaving office.
E. Some hierarchically structured companies have been major financial supporters of candidates for president.

In my view, the reasoning in this argument is that:
business executives tend to be uncomfortable with compromises and power-sharing, which are inherent in politics  few actually seek to become president themselves.

The hidden assumption is that:
lawyers, military leaders, or full-time politicians tend to be comfortable with compromises and power-sharing.

How to weaken this explanation?
In my view, we can undermine this reasoning in this argument in two ways. On the one hand, we can find other reasons excepting for the listed explanation, such as business executives worry about the safe of the presidents, or business executives enjoy freedom, etc. On the other hand, we can rule out analogue between business executives and the listed candidate including lawyers, military leaders, or full-time politicians. That is to say, if we can sure that some of such candidates are also tired of compromises and power sharing like business executives. The reasoning will be seriously undermined.

After this analysis, we can choose B quickly.


97. A scientific theory is a good theory if it satisfies two requirements: it must accurately describe a large class of observations in terms of a model that is simple enough to contain only a few elements, and it must make definite predictions about the results of future observations. For example, Aristotle’s cosmological theory, which claimed that everything was made out of four elements---earth, air, fire, and water---satisfied the first requirement, but it did not make any definite predictions. Thus, Aristotle’s cosmological theory was not a good theory.

If all the statements in the passage are true, each of the following must also be true EXCEPT:

A. Prediction about the results of future observations must be made by any good scientific theory
B. Observation of physical phenomena was not a major concern in Aristotle’s cosmological theory.
C. For elements can be the basis of a scientific model that is simple enough to meet the simplicity criterion of a good theory.
D. A scientific model that contains many elements is not a good theory.
E. Aristotle’s cosmological theory described a large class of observations in terms of only four elements.

After analysis , we can find that the reasoning in this argument is that:
1> it must accurately describe a large class of observations in terms of a model that is simple enough to contain only a few elements and 2> it must make definite predictions about the results of future observations.ßà A scientific theory is a good theory

So , we can find all of choices except B satisfied with the original meaning.

B is not mentioned in this argument , so we can conclude whether B is also true.
So B is the best answer.

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95. Scientific research that involves international collaboration has produced papers of greater influence, as measured by the number of times a paper is cited in subsequent papers, than has research without any collaboration. Papers that result from international collaboration are cited an average of seven times, whereas papers with single authors are cited only three times on average. This difference shows that research projects conducted by international research teams are of greater importance than those conducted by single researchers.

Which one of the following is an assumption on which the argument depends?

A. Prolific writers can inflate the number of citations they receive by citing themselves in subsequent papers.
B. It is possible to ascertain whether or not a paper is the product of international collaboration by determining the number of citations it has received.
C. The number of citations a paper receives is a measure of the importance of the research it reports.
D. The collaborative efforts of scientists who are citizens of the same country do not produce papers that are as important as papers that are produced by international collaboration.
E. International research teams tend to be more generously funded than are single researchers.

In my view, the reasoning in this argument is that:
Papers that result from international collaboration are cited an average of seven times, whereas papers with single authors are cited only three times on average.à research projects conducted by international research teams are of greater importance than those conducted by single researchers.

The hidden assumption is that we can evaluate the importance of research projects by the number of times a paper is cited in subsequent papers.

Obviously, C is the best answer.

A. is out of scope. We can also have good reasons to doubt whether the prolific writers is representative enough to reflect the whole situation of the single authors.
B. the same mistake. Even we can ascertain whether or not a paper is the product of international collaboration by determining the number of citations it has received. The preceding assumption have no effect on the conclusion.
C. is the best answer.
D. is absurd. We have not known anything about the domestic or the alien authors.
E. is out of scope too. There is nothing relevant to fund in this argument.

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94. When 100 people who have not used cocaine are tested for cocaine use, on average only 5 will test positive. By contrast, of every 100 people who have used cocaine 99 will test positive. Thus, when a randomly chosen group of people is tested for cocaine use, the vast people is tested for cocaine use, the vast majority of those who test positive will be people who have used cocaine.

A reasoning error in the argument is that the argument

A. attempts to infer a value judgment from purely factual premises
B. attributes to every member of the population the properties of the average member of the population
C. fails to take into account what proportion of the population have used cocaine
D. ignores the fact that some cocaine users do not test positive
E. advocates testing people for cocaine use when there is no reason to suspect that they have used cocaine

CR will get more interesting when math is involved. The most seen math problem in GMAT CR is percentage. What ETS wants to test is whether you can distinguish between absolute value and relative value, e.g. percentage.
What you need to remember is that higher percentage in CR does not indicate that the absolution number or quantity will be higher compared to lower percentage. To the contrary, higher percentage always has smaller numbers or quantity.
In this question, the conclusion is the last sentence. The premises are that 5% of non-users and 99% of users are tested positive. The argument fails to consider the composition of population and makes an unwarranted assumption that among a random group of people, non-users are less than 99/5 of users. X: non-users Y: users. 5%X < 99%Y è x<99/5Y. If this proportion is not true, the argument does not hold.
So you need to know whether the question is about absolute value or relative value. If it is about relative value, you need to know what the BASE is. If comparison is involved, you need to find out the relationship between the bases.

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92. Baking for winter holidays is a tradition that may have a sound medical basis. In midwinter, when days are short, many people suffer from a specific type of seasonal depression caused by lack of sunlight. Carbohydrates, both sugars and starches, boost the brain’s levels of serotonin, a neurotransmitter that improves the mood. In this respect, carbohydrates act on the brain in the same way as some antidepressants. Thus, eating holiday cookies may provide an effective form of self-prescribed medication.

Which one of the following can be properly inferred from the passage?

A. Seasonal depression is one of the most easily treated forms of depression.
B. Lack of sunlight lowers the level of serotonin in the brain.
C. People are more likely to be depressed in midwinter than at other times of the year.
D. Some antidepressants act by changing the brain’s level of serotonin.
E. Raising the level of neurotransmitters in the brain effectively relieves depression.

从这句话, boost the brain’levels of serotonin, a neurotransmitter that improves the mood, 得知, 只是serotonin有抗忧郁的作用, 而不是所有的neurotransmitter.
D is correct.
A，most easily treated forms和原文无关
B，没有提到的无关信息
C，无关比较
E，把原文的信息扩大范围了，原文说的是a neurotransmitter， E中变成了所有neurotransmitters。


93. The efficiency of microwave ovens in destroying the harmful bacteria frequently found in common foods is diminished by the presence of salt in the food being cooked. When heated in a microwave oven, the interior of unsalted food reaches temperatures high enough to kill bacteria that cause food poisoning, but the interior of salted food does not. Scientists theorize that salt effectively blocks the microwaves from heating the interior.

Which one of the following conclusions is most supported by the information above?

A. The kinds of bacteria that cause food poisoning are more likely to be found on the exterior of food than in the interior of food.
B. The incidence of serious food poisoning would be significantly reduced if microwave ovens were not used by consumers to cook or reheat food.
C. The addition of salt to food that has been cooked or reheated in a microwave oven can increase the danger of food poisoning.
D. The danger of food poisoning can be lessened if salt is not used to prepare foods that are to be cooked in a microwave oven.
E. Salt is the primary cause of food poisoning resulting from food that is heated in microwave ovens.

In my view, the reasoning in this argument is that:
On the one hand:
the presence of salt in the food being cookedà salt effectively blocks the microwaves from heating the interiorà The efficiency of microwave ovens in destroying the harmful bacteria frequently found in common foods is diminished
On the other hand:
unsalted food is heated by microwaveà the interior of unsalted food reaches temperatures high enoughà kill bacteria that cause food poisoning

So , D is the best choice.

A. is out of scope because the exterior of food is not mentioned in this argument.
B. is also out of scope too. We never know what will happen if microwave ovens were not used by consumers to cook or reheat food. Because the statement have no the relevant information.
C. is puzzle. The statement just infers that the harmful bacteria frequently found in common foods is keep same. The salt only prevent microwave from destroying such bacteria. Even though the addition of salt to food will significantly prevent the efficiency of microwave ovens, we can not reach the conclusion that the addition of salt to food that has been cooked or reheated in a microwave oven can increase the danger of food poisoning. So C is problematic choice.
D. is the best choice.
E. may be the extreme pole. The statement not mention that salt is the primary cause of food poisoning resulting from food. It is possible that salt is the relevant factor in determining the efficiency of microwave ovens.

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91. Leachate is a solution, frequently highly contaminated, that develops when water permeates a landifill’s site. If and only if the landfill’s capacity to hold liquids is exceeded does the leachate escape into the environment, generally in unpredictable quantities. A method must be found for disposing of leach ate. Most landfill leachate is sent directly to sewage treatment plants, but not all sewage plants are capable of handling the highly contaminated water.

Which one of the following can be inferred from the passage?

A. The ability to predict the volume of escaping landfill leachate would help solve the disposal problem.
B. If any water permeates a landfill, leachate will escape into the environment.
C. No sewage treatment plants are capable of handling leachate.
D. Some landfill leachate is sent to sewage treatment plants that are incapable of handling it.
E. If leachate does not escape from a landfill into the environment, then the landfill’s capacity to hold liquids has not been exceeded.

此题为充要条件的逆否命题。
A是B的充要条件，那末他的逆否命题比正确！ 非B推出非A

If and only if the landfill’s capacity to hold liquids is exceeded does the leachate escape into the environment, ---------〉If leachate does not escape from a landfill into the environment, then the landfill’s capacity to hold liquids has not been exceeded.

参考答案E
思路：原文说：“Leachate（浸析液）是一种水渗透过垃圾填埋地后生成的溶液，这种溶液通常是高度污染的。当且仅当超出垃圾填埋的容水能力时（A），Leachate会泄露到外界环境中（B）。必须找到一种处理L的方法。许多L被送去用于污水灌溉，但不是所有的污水灌溉的植物都有能力处理这种被高度污染的水”。
原文中If and only if A then B(从B可推出A)；选项E为If not A then not B（非A推非B）正确

A. 原文没有说
B. 条件不对
C. 原文是一部分plants没有这种能力
D. 原文只说明并非所有的污水灌溉的植物都有能力处理这种被高度污染的水，没说some Leachate一定是被送去浇那些无此能力的植物。

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90. Current legislation that requires designated sections for smokers and nonsmokers on the premises of privately owned businesses is an intrusion into the private sector that cannot be justified. The fact that studies indicate that nonsmokers might be harmed by inhaling the smoke from others’ cigarettes is not the main issue. Rather, the main issue concerns the government’s violation of the right of private businesses to determine their own policies and rules.

Which of the following is a principle that, if accepted, could enable the conclusion to be properly drawn?

Government intrusion into the policies and rules of private businesses is justified only when individuals might be harmed.
The right of individuals to breathe safe air supersedes the right of businesses to be free from government intrusion.
The right of businesses to self-determination overrides whatever right or duty the government may have to protect the individual.
It is the duty of private businesses to protect employees from harm in the workplace.
Where the rights of businesses and the duty of government conflict, the main issue is finding a successful compromise.

Current legislation that requires designated sections for smokers and nonsmokers on the premises of privately owned businesses is an intrusion into the private sector that cannot be justified (conclusion from the argument). The fact that studies indicate that nonsmokers might be harmed by inhaling the smoke from others’ cigarettes is not the main issue (refute a possible reason that could be used to counter the conclusion). Rather, the main issue concerns the government’s violation of the right of private businesses to determine their own policies and rules (induce reason for the conclusion to be drawn).

A，反对原文论证
B，反对原文论证
C，答案，it makes clear that the right of business is more important than the duty for government to protect individual, building a bridge for the conclusion to be drawn.
D，无关
E，无关

TEST 6

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89. Rhizobium bacteria living in the roots of bean plants or other legumes produce fixed nitrogen, which is one of the essential plant nutrients and which for non-legume crops, such as wheat, normally must be supplied by applications of nitrogen-based fertilizer. So if biotechnology succeeds in producing wheat strains whose roots will play host to Rhizobium bacteria, the need for artificial fertilizers will be reduced.

The argument above makes which one of the following assumptions?

A. Biotechnology should be directed toward producing plants that do not require artificial fertilize.
B. Fixed nitrogen is currently the only soil nutrient that must be supplied by artificial fertilizer for growing wheat crops.
C. There are no naturally occurring strains of wheat or other grasses that have Rhizobium bacteria living in their roots.
D. Legumes are currently the only corps that produce their own supply of fixed nitrogen.
E. Rhizobium bacteria living in the roots of wheat would produce fixed nitrogen.

参考答案：E
思路：原文的结论是“如果生物工程可以成功培育出能寄生根瘤菌的小麦品种，对人工肥料的需求就会减少”；“生活在大豆或其它豆科植物根部的根瘤菌产生固氮（一种重要的植物养份）”是结论的major premise，应该在二者之间搭桥建立联系，即小麦上寄生的根瘤菌同样能产生固氮。

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88. Court records from medieval France show that in the years 1300 to 1400 the number of people arrested in the French realm for “violent interpersonal crimes” (not committed in wars) increased by 30 percent over the number of people arrested for such crimes in the years 1200 to 1300. If the increase was not the result of false arrests, therefore, medieval France had a higher level of documented interpersonal violence in the years 1300 to 1400 than in the years 1200 to 1300.

Which one of the following statements, if true, most seriously weakens the argument?

A. In the years 1300 to 1400 the French government’s category of violent crimes included an increasing variety of interpersonal crimes that are actually nonviolent.
B. Historical accounts by monastic chroniclers in the years 1300 to 1400 are filled with descriptions of violent attacks committed by people living in the French realm.
C. The number of individual agreements between two people in which they swore oaths not to attack each other increased substantially after 1300.
D. When English armies tried to conquer parts of France in the mid-to late 1300s, violence in the northern province of Normandy and the southwestern province of Gascony increased.
E. The population of medieval France increased substantially during the first five decades of the 1300s, until the deadly bubonic plague decimated the population of France after 1348.
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参考答案：A
思路：他因削弱。
A. “1300-1400年间，法国政府的暴力罪范畴将越来越多的非暴力人际关系罪包括在内。”
B. “在有关1300-1400的历史记述中，充满了关于法国境内居民进行暴力攻击的描述。”无关选项。
C. “1300年以后，二人之间立誓不去互相攻击对方的个人协议大量增加。”无关选项，不能说明犯罪案件是否增加（协议增加可能会使犯罪减少，也可能因为犯罪增加导致协议增多）
D. “1300年中期至末期，在英国军队试图征服法国时，诺曼底北部省份及加斯科涅西南部省份的暴力犯罪有所上升” 支持结论
E. “致命的黑死病使法国人口在1348后大量减少，在此之前，14世纪前50年中法国人口大量增加” 无关选项，人口增加与人际关系犯罪案件上升无必然联系。

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87. A survey was recently conducted among ferry passengers on the North Sea. Among the results was this: more of those who had taken anti-seasickness medication before their trip reported symptoms of seasickness than those who had not taken such medication. It is clear, then, that despite claims by drug companies that clinical tests show the contrary, people would be better off not taking anti-seasickness medications.

Which one of the following, if true, would most weaken the conclusion above?

A. Given rough enough weather, most ferry passengers will have some symptoms of seasickness.
B. The clinical tests reported by the drug companies were conducted by the drug companies’ staffs.
C. People who do not take anti-seasickness medication are just as likely to respond to a survey on seasickness as people who do.
D. The seasickness symptoms of the people who took anti-seasickness medication would have been more severe had they not taken the medication.
E. People who have spent money on anti-seasickness medication are less likely to admit symptoms of seasickness than those who have not.

The passage concludes that the medicine is not useful at all because the people taking the drug appear to be sicker than those people not taking the drug. However, it does not consider the people taking the drug could appear to be even sicker if they do not take the drug. It does not make the wise comparison between two originally the same survey group. So D most accurately point out the lope hole in the reasoning of the passage, thus the best answer.

A. By eliminating the difference of the two survey groups, actually support the conclusion.
B. Without further information, the conclusion will not be changed a little whoever conducted the test.
C. By eliminating the difference of the two survey groups, weakly support the conclusion.
D. As discussed.
E. By even further decrease the sampling difference, E actually support the conclusion.

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85. Which one of the following most accurately expresses the method used to counter the automakers’ current position?

A. The automakers’ premises are shown to lead to a contradiction.
B. Facts are mentioned that show that the automakers are relying on false information.
C. A flaw is pointed out in the reasoning used by the automakers to reach their conclusion.
D. A comparison is drawn between the automakers’ current position and a position they held in the past.
E. Evidence is provided that the new emissions legislation is both economically feasible and environmentally necessary.

The automakers use the reason that these new restrictions would be overly expensive. However, in the past, the automakers previously also used the same reason and their position is proved to be wrong. Consequently the passage draws a comparison, that is, an analogy to disprove the reasoning of the automakers. Thus, D, a comparison is drawn between the automakers’ current position and a position they held in the past, is the most accurate and thus the best choice.

A. The automakers’ premises are not shown to lead a contradiction. Actually if the premises are true, they support their standing point.
B. There is no fact to show that the automakers are relying on false information.
C. The automakers’ reasoning itself does not contain error. The reasoning could only be shown not correct when confronted with past case.
E. There is no evidence that is provided for such purpose here in the passage.

86. Which one of the following, if true, lends the most support to the automakers’ current position?

A. The more stringent the legislation restricting emission becomes, the more difficult it becomes for automakers to provide the required technology economically.
B. Emissions-restriction technology can often be engineered so as to avoid reducing the efficiency with which an automobile uses fuel.
C. Not every new piece of legislation restricting emission requires new automotive technology in order for automakers to comply with it.
D. The more automobiles there are on the road, the more stringent emission restrictions must be to prevent increased overall air pollution.
E. Unless forced to do so by the government, automakers rarely make changes in automotive technology that is not related to profitability.

The automakers’ currently contends that these new restrictions would be overly expensive. If the situation is still the same, if there is no increased difficulty for the automakers to reach the difficulty, the reason here mentioned by them would be simply a scapegoat here for them to escape the necessary effort. However, if the truth is as said in choice A, the more stringent the legislation restricting emission becomes, the more difficult it becomes for automakers to provide the required technology economically, which means that because the current situation asks for even more advanced technology and the increased difficulty could not be overcome economically, the protest of the automakers is well supported.

B. actually weakens the automakers’ current position
C. it has nothing to do with supporting the automakers’ current position. Actually this claim could only express that the automakers do not need to protest that much.
D. If provided together with other information, such as “there are more and more cars on the roads”, the claim of D could serve as a weakening the automakers’ current position.
E. It only makes clear about why necessary for government to intervene and how to realize the plan about reducing the air pollution; in fact, it does not weaken or strengthen the automakers’ current position.