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题库 / Prep2012-CR-40
In the late 1980s, 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?
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.
There is no indication that substantial numbers of sea otters migrated to other locations from the North Pacific in the 1980s.
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.
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.
The North Pacific populations of seals and sea lions cover a wider geographic area than does the population of sea otters.
果因推理 看成类比推理了，a有某种性质 b也有某种性质，b 结论C，那么推出A结论也是C ，这里没有说相似性 只是给出了一个原因，其他生物是疾病导致的
果因推理: whale没有seals and sea lions 吃了，开始吃otters了（他因). 所以disease不是原因，whale才是原因
P：结果 sea otters in the North Pacific Ocean began to decline. seals and sea lions was almost certainly caused by a pollution-related disease,
C：原因 disease is the more likely
A； 鲸鱼没有seals and sea lions 吃了，开始吃其他食物它因削弱。
果因，提出另一种可能：不是疾病引起了otters的减少，而是杀人鲸引起。
果因。
果因