[语法初识]

原句感知 自主探究 ①Many people think the monster may be a distant cousin of the Loch Ness monster in Scotland.

②They also think that there might be similar creatures in other lakes around the world.

③John hasn't come yet, he may have got lost.

④You might have given your parents more help earlier.

⑤Nobody answered the doorbell; he must have gone out.

⑥Mary can't have stolen your money. She has gone home.

⑦You ought to/should have done the job more carefully.

⑧You oughtn't to/shouldn't have asked such a foolish question. 1.①②句表示可能性的推测，意为"可能，也许"。

2．③④句表示对过去发生的事情的推测，意为"可能已经"。

3．⑤句表示对过去事情的很有把握的肯定推测，意为"肯定做过某事"，而⑥句则表示对过去发生事情的很有把握的否定推测，意为"不可能做过某事"。

4．⑦句表示"过去本该做却未做的事"，⑧句则表示"过去本不该发生却发生了的事"。 　　[语法剖析]

语 法 点 "情态动词＋have done"的用法 　　

　　一、表示对过去发生之事的推测

　　可这样用的情态动词有：

　　1．must＋have done表示对过去发生的事情的肯定推测，译成"一定做过某事"，该结构只用于肯定句中。

　　It's surprising that you can drive. You must have learned it before.

　　真没想到你还会开车，你以前肯定学过。

　　2．can/could＋have done，一般用于否定句或疑问句中，表示对过去发生的事情的推测。

　　She can't have left school, for her bike is still here.

　　她一定没离开学校，因为她自行车还在这儿。

　　There is no light in the room. Can they have gone out?

　　屋里没有灯，他们可能出去了吗？

　　3．may/might have done，一般用于肯定句或否定句中，意思是"可能已经"或"也许已经"。

　　He may not have finished the work.

　　他也许还没完成那项工作。

集中演练1