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/mustn't,; can/cann't; need/needn't; may/mayn't; might/mightn't; should/shouldn't; ought等情态动词+完成式表示的意思是有一定区别的
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
2) can't / couldn't 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. couldn't have received B. ought to have received
C. has received D. shouldn't have received
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 Power's Crystal River plant, a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.
1) needn't have +过去分词,表示做了不必做的事,相当于”didn't need to do”,译为“其实没必要……”。如:
You needn't e over yourself.
As it turned out to be a small house party, we so formally.
A. needn't dress up B.did not need have dressed up
C. did not need dress up D. needn't have dressed up
2) should have +过去分词,表示应该做某事但实际上未做,译为“本应该……”should not + have过去分词表示本不应该做某事但实际上做了,译为“本不应该……”。如:
I regret having left the work unfinished; I should have planned everything ahead carefully.
3) ought to have +过去分词,表示动作按理该发生了,但实际上未发生,译为“该……”,与should的完成式含义类似。如:
The porter ought to have called the fire-brigade as soon as he saw the fire in the stock, which went up in smoke.
4) could have +过去分词,表示过去本来可以做但却未做,译为“完全可以……”。这点与ought/should/ have +过去分词用法相似。如:
What you said is right, but you could have phrased it more tactfully.
5) may/ might have +过去分词,表示过去可以做但实际未做,译为“(那样)也许会……”。如: