大家都知道GMAT考试中会对考生的逻辑思维能力进行考核，其实在
81. Nuclear fusion is a process whereby the nuclei of atoms are joined, or “fused”, and in which energy is released. One of the by-products of fusion is helium-4 gas. A recent fusion experiment was conducted using “heavy” water contained in a sealed flask. The flask was, in turn, contained in an air-filled chamber designed to eliminate extraneous vibration. After the experiment, a measurable amount of helium-4 gas was found in the air of the chamber. The experiments cited this evidence in support of their conclusion that fusion had been achieved.
Which one of the following, if true, would cast doubt on the experimenters’ conclusion?
A. Helium-4 was not the only gas founding the experiment chamber.
B. When fusion is achieved, it normally produces several by-products, including tritium and gamma rays.
C. The amount of helium-4 found in the chamber’s air did not exceed the amount of helium-4 that is found in ordinary air.
D. Helium-4 gas rapidly breaks down, forming ordinary helium gas after a few hours.
E. Nuclear fusion reactions are characterized by the release of large amount of heat.
参考答案：C
思路：FACT: nuclear fusion产生H-4. 现象：某个试验有he-4,结论：试验中有nuclear fusion.
驳斥方向：
1. 断桥。有h4推不出nuclear fusion，不过本题无法断桥，因为这是个Fact.
2. 他因，试验中的h4有其他来源。
A. 无关
B. 无关，和A说的同一件事情。
C. 他因。试验中h4 是本来就有的。
D. 无关，本句中心是helium gas 不是h-4。Helium 属于文中没用提的东东，虽然都是helium.
E. 无关，陷阱。试验中完全可能有大量的热，作者没用说，谁也不知道有没有热。
82. Every photograph, because it involves the light rays that something emits hitting film, must in some obvious sense be true. But because it could always have been made to show things differently than it does, it cannot express the whole truth and, in that sense, is false. Therefore, nothing can ever be definitively proved with a photograph.
Which one of the following is an assumption that would permit the conclusion above to be properly drawn?
A. Whatever is false in the sense that it cannot express the whole truth cannot furnish definitive proof.
B. The whole truth cannot be known.
C. It is not possible to determine the truthfulness of a photograph in any sense.
D. It is possible to use a photograph as corroborative evidence if there is additional evidence establishing the truth about the scene photographed.
E. If something is being photographed, then it is possible to prove definitively the truth about it.
参考答案：A
思路：
前提：the photograph in some obvious sense be true, but it cannot express the whole truth .
推论：nothing can ever be definitively proved with a photograph. The problem is which of the following can permit the conclusion be properly drawn.
A. what cannot express the whole truth cannot furnish definitive proof. Right!
B. it is obviously wrong
C. sometimes the photograph cannot express the whole truth but not in any sense. Wrong.
D. this sentence said that photograph can use as an extra evidence for the truth, but it is no relations with the problem.
E. it is obviously wrong according to the passage.
Questions 83-84
Some cleaning fluids, synthetic carpets, wall paneling, and other products release toxins, such as formaldehyde and benzene, into the household air supply. This is not a problem in well-ventilated houses, but it is a problem in houses that are so well insulated that they trap toxins as well as heat. Recent tests, however, demonstrate that houseplants remove some household toxins from the air and thereby eliminate their danger. In one test, 20 large plants eliminated formaldehyde from a small, well-insulated house.
83. Assume that a person who lives in a small, well-insulated house that contains toxin-releasing products places houseplants, such as those tested, in the house.
Which one of the following can be expected as a result?
A. There will no longer be any need to ventilate the house.
B. The concentration of toxins in the household air supply will remain the same.
C. The house will be warm and have a sage air supply.
D. If there is formaldehyde in the household air supply, its level will decrease.
E. If formaldehyde benzene are being released of each will decrease.
参考答案：D
思路：the passage point out that something will release toxins into the air. This is not a problem in well-ventilated houses but a problem in insulated houses. But houseplants can remove some household toxins from the air. In one test 20 large plants eliminated one kind of toxins from a small well-insulated house.
The problems is a person live in a small ,well-insulated house that contains toxin-releasing products. We places some houseplants in the house as those tested. Which one can be a result?
A. we can not include from the passage that houseplants can eliminate all kinds of toxins from the house so ventilation is needed in some way.
B. formaldehyde will be eliminated and the concentration of toxins won’t remain the same.
C. make reference to A
D. it can conclude from the passage! Right!
E. make reference to A
84. The passage is structured to lead to which one of the following conclusions?
A. Houseplants can remove benzene from the air.
B. Nonsynthetic products do not release toxins into houses.
C. Keeping houseplants is an effective means of trapping heat in a poorly insulated house.
D. Keeping houseplants can compensate for some of the negative effects of poor ventilation.
E. The air in a well-insulated house with houseplants will contain fewer toxins than the air in a well-ventilated house without houseplants.
参考答案：D
思路：the problem is which one of the following is truth concluded from the passage!
A. we can not include from the passage that houseplants can eliminate all kinds of toxins from the house. Benzene is not mentioned above. Wrong!
B. the passage does not mention which kind product don’t release toxins. Wrong!
C. including from the passage that houseplants can eliminate one kind of toxins , formaldehyde ,from the house but can not trap heat. Wrong!
D. right! Ventilation is better than keeping houseplants in a house.
E. wrong, just the opposite.
Questions 85-86
In opposing the 1970 Clean Air Act, the United States automobile industry argued that meeting the act’s standards for automobile emissions was neither economically feasible nor environmentally necessary. However, the catalytic converter, invented in 1967, enabled automakers to meet the 1970 standards efficiently. Currently, automakers are lobbying against the government’s attempt to pass legislation that would tighten restrictions on automobile emissions. The automakers contend that these new restrictions would be overly expensive and unnecessary to efforts to curb air pollution. Clearly, the automobile industry’s position should not be heeded.
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.