47 PREP变体
我那题最后的结论是这动物还是被 killer whales吃了，然后问题问的是加强，我选的是在另一个某某地的这种动物确实被killer whales 吃了
参考背景资料
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.作者: 小兔牙 时间: 2010-5-12 15:27
