In the late 1980’s, the population of sea otters in the North Pacific Ocean began to decline. Of the two plausible explanations for the decline—increased predation by killer whales or disease—disease is the more likely. After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease, which could have spread to sea otters, whereas the population of killer whales did not change noticeably.
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 substantial numbers of sea otters migrated to other locations from the North Pacific in the 1980’s.
C.    Along the Pacific coast of North America in the 1980’s, 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.

答案正确是A~~

请给出答案的TX把做题的第一时间思维过程也一并发上来～～～～～～

感觉选A
疾病是导致seals and sea lions数量减少的原因，但并非是导致sea otters 数量减少的原因

A给出他因，sea otters 数量减少是因为killer whales没食物吃，只能吃sea otters

和TX探讨一下思路哦：
大家能不能说一下，觉得题干部分的逻辑结构是怎么样的呢？after all 是起到怎样的作用呢？

题目究竟是要我们削弱的是什么呢？？？

我说一下我的。大家多多贡献一下自己的思路哦～～～～
我看到题后的第一思路反应是：
sea otters数量在减少有两个原因：1. killer whales 2.disease.
但文本认为：disease更可能。
因为1. seals and sea lions 的数量也减少了，减少的原因是他们得了pollution-related

disease。2. killer whales没有减少。

而A是想说明killer whales会使sea otters数量减少，所以削弱了原观点认为的disease是导

致sea otter减少的主因的观点？

思路有待TX们一起鉴定～～～做题关键不在答案在分析，分析怎么能在考试的时候最快地把题

目做对做准～～～对吧～～～～
请各位NN鉴定咯～～～～～～～～～～～～
如果有更好的解题思路也请贴出来，我们可以共同讨论讨论～～～～