7.9 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。