不定式或不定式短語的用法：

不定式在句子中可作主語、表語、賓語、定語、狀語和補(bǔ)足語。

1．作主語

不定式或不定式短語作主語時(shí)，謂語動(dòng)詞用第三人稱單數(shù)。如：

To serve the people well is our duty.

To get there on foot will take several hours.

動(dòng)詞不定式短語作主語時(shí)，往往放在謂語動(dòng)詞的后面，用引導(dǎo)詞it作形式主語。上述兩句也可改為：

It is our duty to serve the people well.

It will take several hours to get there on foot.

(take – need需要(多少時(shí)間等))

類似這樣不定式做主語的句型:

It is + n.+ to do

It a\takes sb.+ some time + to do

It is +adj.+ for sb.+ to do

It is +adj.+ of sb.+ to do

It is our duty to help them.

It will take you quite a long time to finish it.

(finish - fulfill完成)

It is easy for us to answer this question.

It is kind of you to help me

(help –aid 幫助)