In the late 1980's, the population of sea otters in the North Pacific Ocean began to decline. Of the two plausible explaination for the decline-increased predation by killer whales or diease-diease is more likely. After all, a concurrent sharp decline in the populations of seals and sea lions was almost certainly caused by a pollution-related diease, which could could have spead to sea otters, whhereas the population of killer whales did not change noticeably.
Which of the following, if true, would most seriously weaks 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 North Pacific in the 1980's
C.Along the Pacific coast of North America in the 1980's, sea otter were absent from many locations where they had been relatively common in the formerly 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
哪位好心人士，帮忙解答下，我搞了半天，都要晕了。。
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