三、不定式作介词的宾语
介词后接不定式只见于少数场合;but 后面通常接带to的不定式:
That was so serious a matter that I had no choice but_________the police.
A） called in B） calling in C） call in D） to call in
这件事很严重,我别无选择,只得叫警察。（B4，1996.1-24， D对)
在do nothing but， can not but， can not help/choose but等之后,接不带to的不定式:
There was nothing we could do but wait. 我们只好等待。
She could not but admit that they were justified in this.她不得不承认,在这件事情上,他们是有道理的。
except之后也接to不定式:
The windows were never opened except to air the room for a few minutes in the morning. 除了早上给房间换换空气,会把窗户打开几分钟外,窗户总是关着的。
但是,在下面句子中,except 之前为动词do，后面的不定式不带to: He will do anything except lend you money. 他什么事情都会做,就是不会借钱给你。
She can do everything except cook. 她什么事情都会做,就是不会做饭。
四、“介词+关系代词+to 不定式”作定语
这一结构中的关系代词通常是which 或 whom:
You will want two trees about ten feet apart， from_________to suspend your tent.
A)there B)them C)which D)where
你将需要两棵相距约10英尺的树,挂你的帐篷。(B4，1995.6-50，C对)(=You will want two trees about ten feet apart to suspend your tent from.)
The professor can hardly find sufficient grounds__________his argument favour of the new theory.
A） which B） on which to base C） to base on which D） which to be base on
（1995考研,B对）教授几乎找不到充分的理由来支持他的新理论。
Because he could not find the right theme on which to center his thought ， his explanation was vague. 由于他找不到集中其思路的恰当的主题,他的解释是含糊不清的。
