陈向东假设部分第8题，36套Exe29套第3题

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It has been hypothesized that much of the matter in the universe is “dark”, i.e, unseen. Studies have shown that galaxies in many galaxy clusters are moving faster with respect to one another than they would if visible stars constituted all their mass. The studies suggest that the galaxies are moving under the gravitational influence of unseen mass in considerable quantity.

A. Measurements of the speed of moving galaxies are extremely unreliable.

B. The workings of gravitational forces are not particularly well understood.

C the aggregate mass of visible stars in the galaxies mentioned above can be estimated with some confidence.

D the general composition of unseen matter in the universe has been determined.

E without exception, the galaxies mentioned above move toward one another

答案是C

1.对C取非，如果不能估计可见星的总质量，那么就不能知道可见星是否组成了星系的全部质量，就不能知道星系的运动速度是否受到影响。可是这和结论的“星系速度受到了大量不可见物质的引力作用的影响"并不影响啊。这个结论取非，应该是“星系速度没有受到大量不可见物质的引力作用的影响”吧？我这里的推理是不是有问题？

2.我有另外一种理解，看看对不对？由于assumption是conclusion的必要条件，所以conclusion是assumption的充分条件，即因为assumption←conclusion，所以conclusion→assumption。也就是说：只要能从conclusion推理出来的选项，就是assumption。常常需要把conclusion和premise结合在一起作为条件，推理出assumption.（我不清楚这一句有没有逻辑问题，但是貌似做题的时候确实是这样）因为本题conclusion是”星系速度受到了大量不可见物质的引力作用的影响“，可以推出”我们知道星系的速度受到了影响“，因此”我们必然能够估计出可见星的质量和整个星系的质量“（否则”我们没法知道星系的速度受到了影响“）。
如果这种conclusion→assumption的推理是正确的（逻辑上我认为是正确的，必要和充分的关系），这种方法应该比取非简单多了吧！对于这种方法，再举一个例子：

Some doomsayers are warning that long-range warming or cooling trends in weather patterns will drastically reduce grain production. More optimistic reports, however, point out that, even if such drifts in average temperature do occur, we should expect little change in grain production because there is little evidence that changes in rainfall patterns will occur. Moreover, for most crops, climate induced yield trends will be masked by both the year-to-year fluctuation of yields and by the enhancement of yields because of technological factors.

Q.Which of the following is an assumption on which the more optimistic reports mentioned in the passage are based?

A.Long-range changes in weather patterns cannot be accurately predicted.
B.The growing of grain is so highly dependent on technological factors that improvements in yield are unlikely, regardless of climatic conditions.
C.Trends in rainfall patterns are more difficult to isolate than are trends in temperature.
D.Long-range warming or cooling trends are more damaging to grain production if they are accompanied by changes in rainfall patterns than if they are not.
E.Long-range cooling trends are potentially more destructive to grain production than are long-range warming trends.       

我对这段话的理解是：因为雨水不变、每年收成的波动和科技能增加收成，这些因素掩盖了气候变化对谷物产量的不利影响，所以谷物产量不会有太大变化。把这一段话作为条件，可以推出D选项是正确的。
A：无法推理出来。
B：跟上述条件是反着的。上述条件肯定了科技增产，这个选项削弱了科技增产。
C：上述条件没有说到孤立考虑某个因素的难易程度。
D：上述条件肯定了雨水不变对维持产量的重要性，因此气候变化并雨水变化更加damaging.
E：上述条件没有提供信息。

3.用上面那种conclusion→assumption的方法，可以排除ABDE。

逻辑题好棘手。。球推荐好的教材！我觉得陈向东这本好多地方看不懂阿

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Hastings‘ contracture is a disorder of the connective tissue in one or both hands, most commonly causing loss of mobility. A survey of thousands of medical-insurance claims found that over 30 percent of people who had one hand operated on for Hastings' contracture underwent surgery a second time for this disorder within three years. Clearly, therefore, a single surgical treatment of Hastings' contracture is often ineffective at providing long-term correction of the disorder.
　　Which of the following, if true, most seriously weakens the argument?
　　(A) The medical-insurance claims did not specie whether the surgery was on the patient's right or left hand.
　　(B) The surgical techniques used to treat Hastings' contracture are identical to those used successfully to treat certain work-related injuries to the hand.
　　(C) A separate survey found that 90 percent of patients operated on for Hastings' contracture report increased hand mobility within one month after the surgery.
　　(D) All of the patients in the survey were required by their insurance companies to seek a second opinion from a qualified surgeon before undergoing the operation.
　　(E) Many people who have Hastings' contracture choose to tolerate its effects rather than undergo the risks of surgery.

这题我的36套上给的答案是D，怎么看坛子上有的答案是A啊？
此题求详解。

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