1. 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。

2. 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。

3. 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.

4. 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.

5. 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.

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 à 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.

98. Compared to nonprofit hospitals of the same size, investor-owned hospitals require less public investment in the form of tax breaks, use fewer employees, and have higher occupancy levels. It can therefore be concluded that investor-owned hospitals are a better way of delivering medical care than are nonprofit hospitals.

Which one of the following, if true, most undermines the conclusion drawn above?

A. Nonprofit hospitals charge more per bed than do investor-owned hospitals.

B. Patients in nonprofit hospitals recover more quickly than do patients with comparable illnesses in investor-owned hospitals.

C. Nonprofit hospitals do more fundraising than do investor-owned hospitals.

D. Doctors at nonprofit hospitals earn higher salaries than do similarly-qualified doctors at investor-owned hospitals.

E. Nonprofit hospitals receive more donations than do investor-owned hospital.

After analysis of the above statement, we can make it clear that the arguer want to establish the casual relationship between the listed factors, including less public investment in the form of tax breaks, fewer employees and higher occupancy levels, and a better way of delivering medical care.

How to undermine this reasoning?

In my view, I think that we can weaken this argument in two ways. On the one hand, we can destroy the casual relationship the arguer wants to create. On the one hand, we can cite the fact that opposite the conclusion the arguer want to come to.

So , taking into account the above analysis , B is sound.

Because B cites the fact opposing the conclusion.

A is out of scope. The statement does not mention the relationship between the number of per bed and the better way of delivering medical care.

C makes the same mistake. The relationship between the fundraising and the better way of delivering medical care.

D is repeating the above flaw. The reasoning that the higher salaries doctors received, the better way of delivering medical care is open to doubt.

Finally, E follows the same way again. The arguer fails to convince us that more donations will lead to the better way of delivering medical care.

99. Concetta: Franchot was a great writer because she was ahead of her time in understanding that industrialization was taking an unconscionable toll on the family structure of the working class.

Alicia: Franchot was not a great writer. The mark of a great writer is the ability to move people with the power of the written word, not the ability to be among the first to grasp a social issue. Besides, the social consequences of industrialization were widely understood in Franchot’s day.

In her disagreement with Concetta, Alicia does which one of the following?

A. accepts Concetta’s criterion and then adds evidence to Concetta’s case

B. discredits Concetta’s evidence and then generalizes from new evidence

C. rejects Concetta’s criterion and then disputes a specific claim

D. disputes Concetta’s conclusion and then presents facts in support of an alternative creterion

E. attacks one of Concetta’s claims and then criticizes the structure of her argumen

How to crack this type of question in LSAT? In my opinion, if you can adjoin the concept of the logical fallacies in AWA, we can solve easily this problem.

I solve this problem by the following way.

If you are Alicia, how can you refute the conclusion of Concetta? Then , we will have to analyze how Concetta reach his conclusion.

The reasoning in the argument of Concetta is that:

she was ahead of her time in understanding that industrialization was taking an unconscionable toll on the family structure of the working classà Franchot was a great writer

Obviously, the Concetta evaluate Franchot by the criteria of whether she was she was ahead of her time in understanding that industrialization was taking an unconscionable toll on the family structure of the working class.

If we can rule out this criterion, the reasoning of Concetta is unfounded.

Or, even though she was ahead of her time in understanding that industrialization was taking an unconscionable toll on the family structure of the working class, the criteria is insufficient to the brilliance of Franchot.

So, C is the only selection.

Questions 100-101

Zelda: Dr. Ladlow, a research psychologist, has convincingly demonstrated that his theory about the determinants of rat behavior generates consistently accurate predictions about how rats will perform in a maze. On the basis of this evidence, Dr. Ladlow has claimed that his theory is irrefutably correct.

Anson: Then Dr. Ladlow is not a responsible psychologist, Dr. Ladlow’s evidence does not conclusively prove that his theory is correct. Responsible psychologists always accept the possibility that new evidence will show that their theories are incorrect.

100. Which one of the following can be properly inferred from Anson’s argument?

A. Dr. Ladlow’s evidence that his theory generates consistently accurate predictions about how rats will perform in a maze is inaccurate.

B. Psychologists who can derive consistently accurate predictions about how rats will perform in a maze from their theories cannot responsibly conclude that those theories cannot be disproved.

C. No matter how responsible psychologists are, they can never develop correct theoretical explanations.

D. Responsible psychologists do not make predictions about how rats will perform in a maze.

E. Psychologists who accept the possibility that new evidence will show that their theories are incorrect are responsible psychologists.

Let me give you an outline of how I do this question.

1. After reading the question, I know that it is an INFERENCE question. I know that the answer is a REQUIRED condition for the conclusion.

2. Read the argument and understand that the Anson’s conclusion is: Dr. Ladlow is not a responsible psychologist. The premise is: a. research was not conclusive, and b. Responsible psychologists always accept the possibility that new evidence will show that their theories are incorrect.

3. Read the choices.

a. Typical wrong answer. It is irrelevant because whether the evidence is accurate or not is not what Anson cares about. It is the conclusiveness of the evidence that he cares about. Whether it is accurate or not, if the two conditions in (2) are met, the doctor is not responsible according to Anson’s argument.

b. Reads like right answer. It follows both 2a and 2b. Use “not” to test it: Psychologists who can derive consistently accurate predictions about how rats will perform in a maze from their theories CAN responsibly conclude that those theories cannot be disproved. It is a statement that directly counters Anson’s argument. So if Not B is true, Anson’s argument does not hold.

c. This is another typical wrong answer. It is contrary to what Anson argues. So it cannot be right. Use “not” to test it and I can see that Not C is in accordance with Anson. So C is not right.

d. D does not follow the reasoning of Anson. Anson does not care about if it is about rats in a maze or birds in a cage. What he cares about is how theories are drawn by psychologists. So D can be removed quickly.

e. Another typical wrong answer. A à B does not equal to B à A. Basic logic error.

101. Anson bases his conclusion about Dr. Ladlow on which one of the following?

A. an attack on Dr. Ladlow’s character

B. the application of a general principle

C. the use of an ambiguous term

D. the discrediting of facts

E. the rejectiion of a theoretical explanation

Questions 102-103

The brains of identical twins are genetically identical. When only one of a pair of identical twins is a schizophrenic, certain areas of the affected twin’s brain are smaller than corresponding areas in the brain of the unaffected twin. No such differences are found when neither twin is schizophrenic. Therefore, this discovery provides definitive evidence that schizophrenia is caused by damage to the physical structure of the brain.

102. Which one of the following is an assumption required by the argument?

(A) The brain of a person suffering from schizophrenia is smaller than the brain of anyone not suffering from schizophrenia.

(B) The relative smallness of certain parts of the brains of schizophrenics is not the result of schizophrenia or of medications used in its treatment.

(C) The brain of a person with an identical twin is no smaller, on average, than the brain of a person who is not a twin.

(D) When a pair of identical twins both suffer from schizophrenia, their brains are the same size.

(E) People who have an identical twin are no more likely to suffer from schizophrenia than those who do not.

答案：B

思路：

题干：assumption

原文：If one schizophrenic，then one smaller。If neither schizophrenic, then no difference. Conclusion: damage to physical structure cause schizophrenic

核心词：schizophrenic 注意：比较是在twin中进行的

我的习惯是从下到上地看选项。

E 无关项

D 原文没有的信息

C扩大了比较范围

A 扩大了比较范围

B ETS最爱：无他因

103. If the statements on which the conclusion above is based are all true, each of the following could be true EXCEPT:

A. People who lack a genetic susceptibility for the disease will not develop schizophrenia

B. Medications can control most of the symptoms of schizophrenics share many of the characteristics found in those of people without the disorder

C. The brains of schizophrenics share many of the characteristics found in those of people without the disorder

D. It will eventually be possible to determine whether or not someone will develop schizophrenia on the basis of genetic information alone

E. Brain abnormalities associated with schizophrenia are the result of childhood viral infections that inhibit the development of brain cells

答案：C

题干： could be true, EXCEPT = must be false (按照老管的方法，找最确定的)

选项(从下到上)：

E 完全超出原文，不能判断

C完全超出原文，不能判断

B完全超出原文，不能判断

A超出原文，不能判断

D 注意文章第一句：“genetically identical”，选项最后一词“alone”。

104. That the policy of nuclear deterrence has worked thus far is unquestionable. Since the end of the Second World War, the very fact that there were nuclear armaments in existence has kept major powers from using nuclear weapons, for fear of starting a worldwide nuclear exchange that would make the land of the power initiating it uninhabitable. The proof is that a third world war between superpowers has not happened.

Which one of the following, if true, indicates a flaw in the argument?

A. Maintaining a high level of nuclear armaments represents a significant drain on a country’s economy.

B. From what has happened in the past, it is impossible to infer with certainty what will happen in the future, so an accident could still trigger a third world war between superpowers.

C. Continuing to produce nuclear weapons beyond the minimum needed for deterrence increase the likelihood of a nuclear accident.

D. The major powers have engaged in many smaller-scale military operations since the end of the Second World War, while refraining from a nuclear confrontation.

E. It cannot be known whether it was nuclear deterrence that worked, or some other factor, such as a recognition of the economic value of remaining at peace.

答案：E

题干：flaw

原文：

Conclusion：policy worked.

Evidence: end of 2 world war ; 3 world war not happen.

casual explanation.

选项：从下到上

E 他因

D 事实陈述 可以作为weaken

C 无关项

B 迷惑项 请注意：原文是从已知的事实来推测导致事实的原因，所以该事实是不能被反对的。

A 无关项

105. A survey of alumni of the class of 1960 at Aurora University yielded puzzling results. When asked to indicate their academic rank, half of the respondents reported that they were in the top quarter of the graduating class in 1960.

Which one of the following most helps account for apparent contradiction above?

A. A disproportionately large number of high ranking alumni responded to the survey.

B. Few, if any, respondents were mistaken about their class rank.

C. Not all the alumni who were actually in the top quarter responded to the survey.

D. Almost all of the alumni who graduated in 1960 responded to the survey.

E. Academic rank at Aurora University was based on a number of considerations in addition to average grades.

【正确答案】A

【解题思路】

本题的类型是解释类，即解释一个客观事实或现象发生的原因。

本题所陈述的客观事实是：参加调查的一半的对象(1960年的男校友)显示他们的成绩排名处于班上的前四分之一。

本题的考点是整体与部分之间的比例关系的逻辑思维。首先可以排除的是选项C和D，选项C说不是所有排名处于前四分之一的男校友参加了调查，选项D说几乎所有的1960年的男校友参加了调查，都更不利于解释已发生的事实，即使这个客观事实发生的可能性减少。选项E说学校的排名除了考虑平均成绩外，还考虑其他很多因素，但至少还是存在排名的，因此与发生的事实风牛马不相及。只有选项A说大量的不成比例的排名在前的男校友参加了调查最好地解释的所发生的客观事实， 选项B即使可能解释所发生的客观事实，也不如A选项为优。