2015考研英语语法冲刺复习--情态动词现在完成式的用法
在考研英语中，语法的学习可以使我们更好的识别句子结构，理解句子。考研英语语复习是一个慢慢学习并积累的过程。掌握了考研英语语法可以使考研考生在考研阅读理解长难句、考研作文中发挥重要作用。情态动词
1.情态动词的现在完成式的用法
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;
ougtht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?”
must be had been must have been had to be
(答案为C)
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.
couldn’t have received ought to have received
has received shouldn’t 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 Power’s Crystal River plant, a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.
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