①他悄悄地进来，以免把他的妻子吵醒。

　　He came in quietly so as not to/in order not to wake his wife.

　　②为了在天黑前到达，我们很早就动身了。

　　In order to arrive/To arrive before dark，we started early.

　　(2)原因状语：跟在某些表示心理变化的形容词后面，如：glad，surprised，amazed，delighted等。

　　We were surprised to find everything changed.

　　发现一切都变了，我们很惊讶。

　　(3)结果状语：表示出人意料的结果，不定式前有逗号和副词only；也可以用于too...to..."太......而不能......"，...enough to..."足够......"和so/such...as to..."如此......以至于......"句型中。

　　I hurried to Professor Wang's house，only to find he was out.

　　我匆忙赶到王教授的家，可是却发现他出去了。

　　He was so tired as to be unable to walk.

　　他累得走不动了。

　　[名师点津]　

　　动词不定式在作表语或补语的形容词后面作状语时，常用主动形式表示被动含义，常见的此类形容词有easy，hard，difficult，pleasant，interesting，comfortable，safe，dangerous，impossible，fit等，该类形容词说明的是不定式的性质。

　　The poem is not easy to translate.

　　这首诗难翻译。

　　The music is pleasant to listen to.

　　这音乐听起来悦耳。

　　[即时训练2]　单句改错

　　①He was too excited to not say a few words.

　　去掉not

　　②His speech was easy understand.

　　understand前加to

③He tried his best to prepare for the contest，only be told it was cancelled.