1)目的狀語(yǔ)

To… only to (僅僅為了),in order to,so as to,so(such)… as to… (如此……以便……)

He ran so fast as to catch the first bus.他飛快地跑以便趕上第一班車(chē)。

I come here only to say good-bye to you.我來(lái)僅僅是向你告別。

2)作結(jié)果狀語(yǔ)，表事先沒(méi)有預(yù)料到的，要放在句子后面。

What have I said to make you angry.

He searched the room only to find nothing.

3)表原因

I’m glad to see you.

典型例題

The chair looks rather hard, but in fact it is very comfortable to ___.

A. sit B. sit on C. be seat D. be sat on

答案：B.如果不定式為不及物動(dòng)詞，其后應(yīng)有必要的介詞。當(dāng)動(dòng)詞與介詞連用時(shí)，常位于"形容詞+動(dòng)詞不定式"結(jié)構(gòu)的末尾。