洛基JJ第5题，海狮和杀人鲸

weixiushiwansui

GWD-8-Q3:

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.

MarilynR

这貌似是一道托福的小作文里的内容哦 应该是A

endless1990

我也觉得是A，请问有没有别的答案

queenie924

b.没有证据显示大量海狸在文中同一时期内出现过大规模迁移。数量下降和海狸自身迁移无关，不是答案。
c.等于把文中的问题重复了一遍，不是答案。
d.因为海狸数量下降，海狸的主要食物海胆数量大量增长。没解释海狸数量如何下降的，不是答案。
e.北大西洋的海豹和海狮的聚积面积分布比海狸广泛的多。也没解释。

就是a.因为环境污染导致海豹和海狮的数量大幅下降，所以以捕食海豹海狮为主要食物的杀人鲸就会像A里说的一样去捕食海狸，那么海狸数量下降就和环境污染导致的疾病无关。

chriswendy35

作者说两个原因导致数量下降

1鲨鱼

2病

又说应该是病占主要原因

因为After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related disease

但是鲨鱼数量没变

题目weakens the reasoning

A说是鲨鱼是主要原因