2012英语四级语法讲义大全：非谓语动词三

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2、不定式的句法功能：
1）作主语：
To finish the work in ten minutes is very hard.
3 ?! [4 Y5 a  z; y" I- uTo lose your heart means failure.动词不定式短语作主语时，常用形式主语it作形式主语，例如上面两句可用如下形式：
It is very hard to finish the work in ten minutes.
3 k* ~" f  o0 u+ EIt means failure to lose your heart.
2）作表语：
; F5 W3 _! N1 A/ R+ rHer job is to clean the hall.
6 N3 K$ D# x, X; |0 iHe appears to have caught a cold.
3）作宾语：
常与不定式做宾语连用的动词有：want, hope, wish, offer, fail, plan, learn, pretend, refuse, manage, help, agree, promise, prefer, 如果不定式（宾语）后面有宾语补足语，则用it作形式宾语，真正的宾语（不定式）后置，放在宾语补足语后面，例如：
$ J' v, h: m, O" k0 gMarx found it important to study the situation in Russia.
+ \# Y+ ]) u: W/ i) \& _5 Y' X动词不定式也可充当介词宾语，如：
- L& I5 \1 C* [4 d& AI have no choice but to stay here.
" N5 Z1 ^; l4 V. FHe did nothing last Sunday but repair his bike.
动词不定式前有时可与疑问词连用，如：
He gave us some advice on how to learn English.