①上述感觉动词与使役动词转换为被动结构时.其后的不定式一般需带to，如：
He was seen to come.
The boy was made to go to bed early.
②在动词find与help之后www.med126.com，不定式可带to亦可不带to，如:
He was surprised to find the sheep (to) break fence at this season.他发现羊在此季节越出栅栏，感到惊讶。
3)在do nothing/anything/everything but(except)结构中。例如：
Last night I did nothing but watch TV.昨天晚上，我除了看电视别的什么也没有干。
但是，如果谓语动词不是“do nothing，anything，everything”，那么but(except)所跟的不定式则仍须带。
The doctor told him nothing but to stop smoking.医生除了让他戒烟，其它什么都没有说。
There was nothing for them to do but to remain silent.除了保持沉默以外，他们没有别有别的办法。
(4)不定式与动名词的逻辑主语和分词独立结构
1)不定式的逻辑主语为：for +名词(或代词宾格)+ 不定式。例如：
I found it impossible for him to do the job alone.我发现他—个人干这活是不可能的。
(注)在表示人物性格、的特性等的形容词后面，常用of引出不定式的逻辑主语。例如：
It was wise of him to do that.他那样做是明智的。
2)动名词的逻辑主语为;①人称代词的所有格+动名词;②名词’s+动名词。例如：
Tom insisted on my going with them.他坚持要我和他们一起去。
He dislikes his wife’s working late.他不喜欢他妻子工作得很晚。
3)某些形容词，如：careless等不定式后可以加of来引导出其逻辑主语。这类词主要有：absurd, bold, brave, courageous, careful, careless, clever, wise, foolish, silly, stupid, good, nice, kind thoughtful, considerate, greedy, generous, honest, modest, polite, rude, cruel ,selfish, wicked, wrong等
It is very kind of you to help me.你帮助我太好了。
间或也可用for + there to be表示(而且there后面的不定式只能是to be)。
It’s a great pity for there to be much trouble in the company.太遗憾了公司里有这么多的麻烦。
