�、偕鲜龈杏X動詞與使役動詞轉(zhuǎn)換為被動結(jié)構(gòu)時.其后的不定式一般需帶to，如：
He was seen to come.
The boy was made to go to bed early.
②在動詞find與help之后f1411.cn，不定式可帶to亦可不帶to，如:
He was surprised to find the sheep (to) break fence at this season.他發(fā)現(xiàn)羊在此季節(jié)越出柵欄，感到驚訝。
3)在do nothing/anything/everything but(except)結(jié)構(gòu)中。例如：
Last night I did nothing but watch TV.昨天晚上，我除了看電視別的什么也沒有干。
但是，如果謂語動詞不是“do nothing，anything，everything”，那么but(except)所跟的不定式則仍須帶。
The doctor told him nothing but to stop smoking.醫(yī)生除了讓他戒煙，其它什么都沒有說。
There was nothing for them to do but to remain silent.除了保持沉默以外，他們沒有別有別的辦法。
(4)不定式與動名詞的邏輯主語和分詞獨立結(jié)構(gòu)
1)不定式的邏輯主語為：for +名詞(或代詞賓格)+ 不定式。例如：
I found it impossible for him to do the job alone.我發(fā)現(xiàn)他—個人干這活是不可能的。
(注)在表示人物性格、的特性等的形容詞后面，常用of引出不定式的邏輯主語。例如：
It was wise of him to do that.他那樣做是明智的。
2)動名詞的邏輯主語為;①人稱代詞的所有格+動名詞;②名詞’s+動名詞。例如：
Tom insisted on my going with them.他堅持要我和他們一起去。
He dislikes his wife’s working late.他不喜歡他妻子工作得很晚。
3)某些形容詞，如：careless等不定式后可以加of來引導出其邏輯主語。這類詞主要有：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.你幫助我太好了。
間或也可用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.太遺憾了公司里有這么多的麻煩。
