动词know后的不定式符号to的省略问题

 

当动词know的后面跟有不定式作宾语补足语时(即用于know+宾语+不定式),该不定式有时带to,有时不带to,具体用法如下:

(1) know为一般现在时,则其后用作宾语补足语的不定式不能省略to(此时的不定式通常为to be型)。如:

I know him to be ill. 我知道他病了。

We know her to be honest. 我们知道她是诚实的。

(2) know为一般过去时或现在完成时,则其后用作宾语补足语的不定式可以省略to,也可以保留to(此时的不定式可以是to be型,也可以是to do型)。如:

I never knew him (to) do such a thing. 我从未听说他会干那种事。

I’ve never known her (to) be late before. 我以前从不知道她迟到过。

I’ve never known it (to) snow in July before. 我从未听说过有七月下雪的事。

I have never known a horse (to) eat fish. 我没听过马会吃鱼。

但是,当用作宾语补足语的不定式为完成式时,其中的to不能省略。如:

They knew the man to have been a thief. 他们发现此人曾是个小偷。

I have never known her to have failed. 我从来没发现她失败过。

(3) 当动词know本身用于被动语态时,其后的不定式不能省略to。如:

He has never been known to tell a lie. 从未有人听说过他说谎。

Smoking is known to increase a person’s risk of developing lung cancer. 据说吸烟会增加一个人患肺癌的风险。

People have been known to drive 500 miles just to visit the shop. 听说有人驾车500英里只是为了去这家商店。

 

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