2012年成人英语三级考试之辅导讲义(三)
三、非谓语动词 不定式（to + V）
动名词
分词-ing
分词-ed
（一）动词不定式（to+动词原形）
动词不定式的语法功能可以做除谓语动词以外的任何句子成分。
（1）作主语
不定式或不定式短语作主语时，谓语动词用第三人称单数。如：
To serve the people well is our duty.
动词不定式短语作主语时，往往放在谓语动词的后面，用引导词it作形式主语。上述句子也可改为：
It is our duty to serve the people well.
类似这样不定式做主语的句型有：
It is + n.+ to do
It takes sb.+ some time + to do
It is +adj.+ for sb.+ to do
It is + adj.+ of sb.+ to do
例如：
It is our duty to help them.
It will take you quite a long time to finish it.
It is easy for us to answer this question.
It is kind of you to help me.
注：
（1）for sb.常用于表示事物的特征特点，表示客观形式的形容词，如easy，hard，difficult，interesting，impossible等：
（2）of sb.的句型一般表示人物 的性格，品德，表示主观感情或态度的形容词，如good，kind，nice，clever，foolish，right等。
（2）作宾语
We hope to have more opportunities to talk with native speakers.
注意：
如果不定式作宾语而又跟有补语，这时，通常要用“it”作形式宾语，而将不定式放到补语后面去。
例如：
他们发现提前把一切都准备好是不可能的。
×They found to get everything ready in advance impossible.
宾语　宾补
×They found to get everything ready in advance is impossible.
√They found it impossible to get everything ready in.
宾补　宾语
advance.
再看下面的两个例句：
I consider it my duty to point out their shortcomings.
Robert doesn“t think it advisable for Mary to be on a diet.