PREP一道削弱逻辑题

超然成风

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.


答案选A，我的思路是作者的结论是因为疾病导致的，给出了原因1，concurrent,seal 和lion 的数量也下降2，前面两者的原因可能是疾病造成的

选A是不是就是否定了原因二，就是说前面两者的死亡不是疾病造成的


而我的第一反应应该是他因或者找办法切断前提和结论之间的关系

hughlv

按我的经验，像这种A导致了B的论点，需要weaken有两个途径：1. 证明A导致不了B；2.证明还有其他导致B的原因。

如果有选项符合条件1，则肯定选该项，否则找符合条件2的选项。