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标题: 请教PREP2 83 [打印本页]

作者: niswzzhn 时间: 2007-12-22 21:16
标题: 请教PREP2 83

83.
(28949-!-item-!-188;#058&004110)

The number of plant and animal species that humans are known to have forced to extinction in the last half millennium is over 800.

(A) humans are known to have forced to extinction

(B) humans are known as having forced to become extinct

(D) are known that humans forced to become extinct

(E) are known as having been forced to extinction by humans

正确答案是A，我想问一下A中的have fored to extinction结构为什么用现在完成时态啊，句子中没有明显的时间标志啊？谢谢大家。

作者: easy4meeeeee 时间: 2007-12-22 23:09

in the last half millennium

in...years

都可以用现在完成时态的

这里的逻辑意思也要求用

作者: niswzzhn 时间: 2007-12-23 22:47
谢谢你，我刚看出来那个结构in the last/past/recent few years。

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