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21.5 must表示推測
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  1) must用在肯定句中表示較有把握的推測,意為"一定"。
  2) must表對現(xiàn)在的狀態(tài)或現(xiàn)在正發(fā)生的事情的推測時, must 后面通常接系動詞be 的原形或行為動詞的進(jìn)行式。
    You have worked hard all day.You must be tired.  你辛苦干一整天,一定累了。(對現(xiàn)在情況的推測判斷)
    He must be working in his office. 他一定在辦公室工作呢。


  比較:
    He must be staying there. 
    他現(xiàn)在肯定呆在那里。
    He must stay there.
    他必須呆在那。
  3) must 表示對已發(fā)生的事情的推測時,must 要接完成式。
   I didn't hear the phone. I must have been asleep. 我剛才沒有聽到電話,我想必是睡著了。


  4) must表示對過去某時正發(fā)生的事情的推測,must 后面要接不定式的完成進(jìn)行式。
   ---Why didn't you answer my phone call?
   ---Well, I must have been sleeping, so I didn't hear it.


  5) 否定推測用can't。
   If Tom didn't leave here until five o'clock, he can't be home yet. 如果湯姆五點才離開這兒,他此時一定還未到家。

















 學(xué)習(xí)啦--英語語法大全