22.
In the late 1980s, the population of sea otters in the North 
acific began to decline. There are two plausible explanations for the decline: predation, possibly by killer whales, or disease. Of these two, disease is the more likely, since a concurrent sharp decline in populations of seals and sea lions is believed to have been caused by disease, and diseases that infect these creatures are likely to be able to infect sea otters also.
逻辑简图：Disease killed seals and lions+disease will infect sea otters-----the explanation for the decline of sea otters is disease
Which of the following, if true, most seriously weakens the reasoning?
(A) Killer whales in the North acific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.(他因，說明應該是第一個原因)
(B) There is no indication that the sea otter population at any North acific location declined in the 1980s because of substantial numbers of sea otters migrating to other locations.（感觉B也能解释啊，也算是一个他因吧）
(C) Along the acific coast of North America in the 1980s, sea otters were absent from many locations where they had been relatively common in former times.
(D) Following the decline in the population of the sea otters, there was an increase in the population of sea urchins, which are sea otters' main food source.
(E) The North acific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.
23.
From 1978 to 1988, beverage containers accounted for a steadily decreasing percentage of the total weight of household garbage in the United States. The increasingly widespread practice of recycling aluminum and glass was responsible for most of this decline. However, although aluminum recycling was more widely practiced in this period than glass recycling, it was found that the weight of glass bottles in household garbage declined by a greater percentage than the weight of aluminum cans.
逻辑简图：aluminum recycling was more widely practiced in this period than glass recycling
VS
the weight of glass bottles in household garbage declined by a greater percentage than the weight of aluminum cans.
Which of the following, if true of the United States in the period 1978 to 1988, most helps to account for the finding?
(A) Glass bottles are significantly heavier than aluminum cans of comparable size.（重量也可以解释啊）
(B) Recycled aluminum cans were almost all beverage containers, but a significant fraction of the recycled glass bottles had contained products other than beverages.
(C) Manufacturers replaced many glass bottles, but few aluminum cans, with plasticcontainers.（他因解釋，就是因為生产厂家都用所料来代替glass了）
(D) The total weight of glass bottles purchased by households increased at a slightly faster rate than the total weight of aluminum cans.
(E) In many areas, glass bottles had to be sorted by color of the glass before being recycled, whereas aluminum cans required no sorting.
37.
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Capuchin monkeys in Venezuela often rub a certain type of millipede into their fur. Secretions of these millipedes have been shown to contain two chemicals that are potent mosquito repellents, and mosquitoes carry parasites that debilitate the capuchins. The rubbing behavior is rare except during the rainy season, when mosquito populations are at their peak. Therefore, the monkeys probably rub the millipedes into their fur because doing so helps protect them against mosquitoes.
逻辑见图：mosquito populations are at their peak during rainy season+ these millipedes have been shown to contain two chemicals that are potent mosquito repellents+rubbing with millipedes behavior is more during the rainy season-----rubbing behavior helps protect them against mosquitoes
Which of the following would it be most useful to determine in order to evaluate the argument?
(A) Whether the two chemicals provide any protection for the millipedes against their own predators
(B) Whether the type of millipede used by the capuchin monkeys in Venezuela is found in other parts of the world
(C) Whether animals other than capuchins rub insects of any kind into their fur
(D) Whether the only time the millipedes are readily available to the capuchins is during the rainy season(找一下是否有他因，如果M只存在于雨季，那么抓他不一定是因為他防蚊)
(E) Whether secretions of any other insects accessible to the capuchins contain chemicals that repel mosquitoes（感觉E是从分泌物的方面来评估。取两个极端的话，好像也能解释通）
49.
An overly centralized economy, not the changes in the climate, is responsible for the poor agricultural production in Country X since its new government came to power. Neighboring Country Y has experienced the same climatic conditions, but while agricultural production has been falling in Country X, it has been rising in Country Y.
X Y have different economy and same climate, the agriculture in X falls and in Y improves-----the centralized economy is the course.
Which of the following, if true, would most weaken the argument above?
(A) Industrial production also is declining in Country X.
(B) Whereas Country Y is landlocked, Country X has a major seaport.(地理位置不算一个他因嘛)
(C) Both Country X and Country Y have been experiencing drought conditions.
(D) The crops that have always been grown in Country X are different from those that have always been grown in Country Y.（他因，因为植物本身就不同）
(E) Country X's new government instituted a centralized economy with the intention of ensuring an equitable distribution of goods.
第一题，它的逻辑不是说因为otter减少了，所以只有两种可能解释。如果是这么reasoning的，那B是对的。但题目的逻辑是otter减少了，有两种可能（不过是叙述情况而已）。所以，因为第一种情况不可能，原因必定是第二种。这里要weaken的是如果第一种不可能，也不一定是第二种。
23，题目问的是most, 所以C比较好啦。玻璃瓶比一样大小的铝瓶重的确是一种可能性，但是不是最好的答案。因为你还得还要一个前提就是：瓶子回收数量上的不足要被它的质量所compensate……但是C的支持作用是直接的。
37题，D是说当雨季来临的时候M是否available，如果哪时候根本没有M，那假设肯定不成立了。E我觉得和提干说的东西无关。
40，提干说了 Neighboring Country Y has experienced the same climatic conditions所以楼主的选项是在驳斥这个条件，而不是结论。
23题 我觉得如果按照jesuischong的解释的话，C也必须有一个前提，之前多出来的这些铝盒就是这些厂家生产的塑料制品所compensate啊。。。
37题我承认D是可以评估的，但是我觉得E也从另外一个角度评估了。(E) Whether secretions of any other insects accessible to the capuchins contain chemicals that repel mosquitoes
如果把这个选项取两个极端的话：1 成立，说明不只是millipedes在分泌可以抑制蚊子的物质，所以猴子抓millipedes的原因不是因为millipedes防蚊。
2不成立，说明只有millipedes分泌防蚊物质，抓他就是为了防蚊
40题的前提是说天气原因被否定，结论所以原因是经济体制。而B并没有否定天气不是原因这个前提，而是提出地理位置这个他因。
37:E选项：成立：说明猴子可以使用多于一种的虫来防蚊。
不成立：说明猴子只有一种虫来防蚊。
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