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标题: prep1-22 [打印本页]

作者: nevaeh11 时间: 2010-10-12 12:46
标题: prep1-22

22.(28829-!-item-!-188;#058&003748)

In the late 1980s, the population of sea otters in the North Pacific 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.

Which of the following, if true, most seriously weakens the reasoning?

(A) Killer whales in the North Pacific usually prey on seals and sea lions but will, when this food source is scarce, seek out other prey.

(B) There is no indication that the sea otter population at any North Pacific location declined in the 1980s because of substantial numbers of sea otters migrating to other locations.

(C) Along the Pacific 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 Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.

谢谢大家

作者: alown 时间: 2010-10-12 22:21
同问，做了两次好像都错了

作者: alown 时间: 2010-10-12 22:28
我自己分析了一下，会不会因为（A）seals和lions的减少，导致killer whales转向其他的猎物，即otters。所以otters的减少不是因为疾病，而是因为killer whales的捕食，从而weaken the reasoning。
求指教。

作者: iSonic 时间: 2010-11-29 03:39
我觉得你说的有道理，我虽然对了，但是是用排除法的，你说服我了

作者: woaihenglia 时间: 2010-11-29 08:45
是a没错，也就是我们所说的外因影响，非题意推测出的原因

作者: 小唯唯 时间: 2011-4-11 20:50
这也太复杂了吧…………那这个“weaken the reasoning”指的是削弱得到“更偏向于生病”这个结论的原因还是对给出两个可能的解释的削弱？？？

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