用作介词的to

　　to 有两种用法：一为不定式+动词原形; 一为介词+名词/动名词， to 在下面的用法中是第二种，即to+ 名词/动名词：admit to承认，confess to承认，be accustomed to 习惯于，be used to 习惯于，stick to 坚持，turn to开始，着手于，devote oneself to 献身于，be devoted to 致力于， look forward to 盼望，pay attention to

　　注意

　　省to 的动词不定式

　　1) 情态动词 ( 除ought 外，ought to)：

　　2) 使役动词 let, have, make：

　　3) 感官动词 see, watch, look at, notice , observe, hear, listen to, smell, feel, find 等后作宾补，省略to。

　　注意

　　在被动语态中则to 不能省掉。

　　I saw him dance. =He was seen to dance。

　　The boss made them work the whole night.=They were made to work the whole night。

　　4) would rather，had better：

　　5) Why… / why not…：

　　6) help 可带to，也可不带to, help sb (to) do sth：

　　7) but和except：but前是动词do时，后面出现的动词用不带to的动词不定式。

　　8) 由and, or和than连接的两个不定式，第二个to 可以省去：

　　9) 通常在discover, imagine, suppose, think, understand等词后，可以省去to be：He is supposed (to be) nice.　他应该是个好人。举例：He wants to move to France and marry the girl. He wants to do nothing but go out. 比较：He wants to do nothing but go out. He wants to believe anything but to take the medicine。

　　典型例题

　　1) ---- I usually go there by train.

　　---- Why not ___ by boat for a change?

　　A. to try going　 B.　trying to go　 C.　to try and go　 D.　try going

　　答案：D. why not 后面接不带to 的不定式，因此选D。

　　2) Paul doesn't have to be made ___. He always works hard.

　　A. learn　 B. to learn　 C. learned　 D. learning

　　答案：B. make后接不带to 的动词不定式，当其用于被动时，to 不可省略。

　　动词不定式的否定式

　　Tell him not to shut the window…

　　She pretended not to see me when I passed by. 我走过的时候，她假装没看见。

　　典型例题

　　1) Tell him ___ the window.

　　A. to shut not　 B. not to shut　 C. to not shut　 D. not shut

　　答案：B。 tell sb to do sth 的否定形式为tell sb not to do sth。

　　2) She pretended ___ me when I passed by.

　　A.　not to see　 B. not seeing　　C. to not see　 D.　having not seen

　　答案：A。 pretend 后应接不定式。其否定形式为pretend not to do sth.。

　　3) Mrs. Smith warned her daughter ___ after drinking。

　　A. never to drive　 B. to never driver　C. never driving　 D. never drive

　　答案：A。warn sb to do sth. 的否定形式为warn sb not to do sth. 此处用的是否定词never。

　　4) The boy wanted to ride his bicycle in the street，but his mother told him ____.

　　A. not to　　B. not to do　　C. not do it D. do not to

　　答案：A。not to 为not to do it 的省略形式。可以只用to这个词，而不必重复整个不定式词组。及物动词do后应有名词、代词等，否则不对，因此B，D不对。

　　5) The patient was warned ___ oily food after the operation。

　　A. to eat no　 B. eating not　 C. not to eat　D. not eating

　　答案：C。warn一词要求后用不定式，此处为不定式的被动，否定形式为be warned not to do。