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英语语法之虚拟语气视频讲解03讲



虚拟语气03讲

  情态动词 + have done   
 
一. “情态动词 + have + done”,表示对过去的行为或动作进行推测。
 
1. “must have done”表示对过去事情的肯定推测,翻译成“一定做过某事”。
     没有mustn’t    have done这一用法。其相对应的否定或疑问句中用的形式是
   “can’t/couldn’t have done”,翻译为“不可能做过某事”。
 
如;  ----Tom often touches people’s stuff without permission. Yesterday he came to my home. 
        He must have touched my things. I don’t like him.
     ----He can’t have touched your things because your room was locked.
 
2. “may / might have done”表示对过去事情的不确定的推测,翻译成“过去可能做了某事”。
    may 比 might 表示的可能性在说话人看来稍大些。
   其相对应的否定形式是may/might not have done,表示“过去可能没有做某事。
   ” may/might have done表推测不用于疑问句中。
 
如: ----He may have heard everything I just said.
        ----Don’t worry. He may not have heard it. 
 
3. “can/could have done” 表推测一般用在否定句和疑问句中,表示不相信或怀疑的态度。
 
如: ----Can/Could she have heard the truth that day?
        ----I think she can’t/couldn’t have heard it because she looked normal.
 
 
二. “情态动词 + have + done”的虚拟语气的用法。
 
1.    could have done, 表示“过去本能够做某事却未做。”
 
注:其否定形式 couldn't have done 没有虚拟语气的用法.
 
如; I could have saved her, but I was too scared. I’m so sorry.
 
2.   Might have done, 表示“过去本可以做某事却未做。” 
 
注:其否定形式 might not have done 没有虚拟语气的用法. 
 
如: I might have saved her. It’s hard to say.
 
3.    needn't have done 表示 “过去本不需要做某事却做了。”
      一般来说need have done这种形式用的很少。
 
如:You are so polite. You needn’t have bought so many things.
       You needn’t have come here personally. 
 
4.   should have done , 表示“过去本应该做某事却未做。”
 
注:其否定结构 shouldn't have done 表示 “过去本不该做某事却做了。”  
 
如: You should have finished your homework.
 
       He should not have done that. It was too stupid. 
 
5.    Would have done, 表示“过去本来会做某事却没做”.
 
注:其否定结构wouldn’t have done表示“过去本不会做某事却做了”。
 
如: I would have attended the sports meeting, but because my foot was injured, I didn’t.
        I wouldn’t have killed the spider, but he forced me to do that. 
 
 
例题讲解:
 
1. I was really anxious about you. You_________ home without a word.   
 
A. mustn't leave                 B. shouldn't have left 
C. couldn't have left           D. needn't leave  
 
2. — I’ll tell Mary about her new job tomorrow.   
    — You________ her last week.  
 
 A.ought to tell                B.would have told
 C.must tell                      D.should have told
 
3. He _______ have completed his work; otherwise, he wouldn't be enjoying himself by the seaside. 
 
A. should          B. must        C. wouldn't        D. can't  
 
4. — Do you know where David is? I couldn't find him anywhere.  
   — Well. He _______have gone far, for his coat's still here. 
 
A.shouldn't       B.mustn't        C.can't        D.wouldn't