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.
问题分析：A说除了原文那两个原因，还有killer whales吃东西，和文章第一个原因有联系，留着。B 说sea otter数量下降的原因是sea otter搬到其他地方去了，文章没说过，杀。C 说sea otters以前数量很多的地方现在都没有了，显然没说过，杀。D 说随着sea otters数量的下降，sea urchin数量上升，整体说的就是sea otters数量多了后，sea otter食物多了（别漏掉尾巴那块的定语从句）E 说seals和lions比sea otters哪个占的地方大，显然没说，杀。
