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标题: 大全550，once [打印本页]

作者: playirrrr 时间: 2007-8-25 11:52
标题: 大全550，once

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

(A) black-footed ferrets are thought to have declined in number as

(B) it is thought that the decline in number of black-footed ferrets is

(D) that black-footed ferrets have declined in their numbers is thought to be

(E) the numbers of the black-footed ferret are thought to have declined as

这道题我始终不理解为什么选A，难道once放在句首有特殊作用，麻烦大家解释一下

作者: Icanw 时间: 2007-8-25 12:37
不是因为once的缘故，而是所有的选项中只有A的主语可以作once从句中 (be/became) commone throughout the Westerm plains的主语。尽管主句用了被动。。。

作者: playirrrr 时间: 2007-8-25 15:29

那C为什么不行呢？、

作者: dudulee 时间: 2007-8-25 17:38
the decline不能做前面句子的逻辑主语

作者: playirrrr 时间: 2007-8-25 19:57
前句的主语是black-footed ferrets 吗？

作者: dudulee 时间: 2007-8-25 20:28
以前在西部平原上很常见，逻辑主语除了是一种动物没有其他东西了吧

作者: lichabrend 时间: 2008-8-20 16:56

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