LZM E8-32

arrymin

对LZM的解释不是很清楚。

Once common throughout the Western plains, (black-footed ferrets are thought to have declined in number) as a result of the poisoning of prarie dogs, their prey.

A
B it is thought that the decline in number of black-footed ferrets is
C the decline in the number of black-footed ferrets is thought of as
D that black-footed ferrets have declined in their numbers is thought to be
E the numbers of the black-footed ferrets are thought to have declined as


我知道解题点在于主谓一致，但不是很明白此题的意思，LZM说ONCE是省略的时间状语，不知道完整的句子是什么，又作何解释？
希望各位高手给予指点，
[em27][em27][em27]

yiyuan05

to have declined用了动词不定式的完成体，表明decline 发生在think之前

arrymin

LZM说由于ONCE引导的时间状语的省略形式决定了主句的主语只能是A,但是到底完整的句子是怎样的呢？此句的中文应该如何翻译？

redli

这句话意是：黑腿雪貂曾经在西部平原很普遍，后来它数量的下降被认为是由于它们的猎物（就是那个DOG）中毒导致的。

cook

The answer is A.
Complete sentence as the following:

Once (black-footed ferrets )common throughout the Western plains, (black-footed ferrets are thought to have declined .....

arrymin

谢谢redli,你的解释非常清楚,还有cook是句子结构非常清楚,但是不是应该在从句中加上were,(once black-footed ferrets were common throughtout the western plains,.....).