情态动词现在完成式主要有两个功能:表示已经发生的情况和表示虚拟语气。在这两个方面must/mustncan/cannneed/neednmay/maynmight/mightnshould/shouldnought等情态动词+完成式表示的意思是有一定区别的
1.表示已经发生的情况。
1)must have+过去分词,表示对已发生情况的肯定推测,译为(昨天)一定。如:
My pain apparent the moment I walked into the room, for the first man I met asked sympathetically: Are you feeling all right?
[A] must be [B] had been [C] must have been [D] had to be
(答案为C)
2)cant / couldnt have+过去分词,表示对已发生情况的否定推测,译为(昨天)一定没。如:
Mary my letter; otherwise she would have replied before now.
[A] couldnt have received [B] ought to have received
[C] has received [D] shouldnt have received
(答案为A)
3)may / might have +过去分词,表示对已发生的事情做不肯定、可能性很小的推测,或事实上根本没发生,译为也许。如:
At Florida Powers Crystal River plant, a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.
2.表示虚拟语气。
1) neednt have + 过去分词,表示做了不必做的事,相当于didnt need to do,译为其实没必要。如:
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