用适当的情态动词表示讲话者对客观事物的主观看法，这就是情态动词的推测性用法。常用来表示推测的情态动词有 might，may，must，can。might，may，must表示的可能性程度由弱变强，must表示"一定"， can则一般用于疑问句或否定句中。例如：
1．They must be talking about us on the radio right now．
此刻，他们一定在电台里谈论我们的情况。
2．She may have missed her train．
她可能没有赶上火车。
3．I don't know why he is late，he might have had an accident．
我不知道他为何迟到，可能遇上了事故。
4．Where can John have put the matches？ He can't have thrown them away．
约翰会把火柴放在哪儿呢？他不可能把火柴扔掉的。
5．That can't be the postman，it's only seven o'clock．
才七点钟，不可能是邮递员。
表示推测的情态动词后的动词不定式可用完成式、进行式和一般式三种。用完成式表示对过去情况的推测。例如：
6．Her father thought that she must have met a fairy．
她父亲认为她一定碰上了仙女。
7．They must have studied English for years．
他们学习英语肯定有几年了。
8．You may have left your glasses at the office．
你可能把眼镜忘在办公室了。
用进行式则表示对正在发生的动作的推测。例如：
9．He might be reading a newspaper now．
他可能正在看报纸。
10．He can't be working at this hour．
这个时候他肯定不会在工作。
推测性情态动词后用不定式的一般式有两种情况：如果不定式是状态动词，则表示对现在状态的推测。如果不定式是动作动词，则表示对将来动作的推测。例如：
11．Mary must have some problem ，she keeps crying．
玛丽不停地哭，一定有了麻烦。
12．I saw that the camel must be blind in the right eye．
我知道这只骆驼右眼肯定瞎了。
13．Our team must win the game．
＝I'm sure that our team will win the game．
我们队肯定能赢这场比赛。
14．It might rain this evening．
＝It's possi- ble that it will rain this evening．
今天傍晚天可能要下雨。
上述表明，推测性情态动词是以现在（讲话时）为基础，对过去、现在、将来的动作或状态的推测。因此，在构成陈述部分含有推测性情态动词的反意疑问句时，要注意反意疑问句中动词的不同形式。例如：
15．The boy must have thought John was mad，didn't he？
那孩子肯定以为约翰疯了，是吗？
16．Our teacher must have looked through our papers，hasn't he？
老师一定批完了我们的试卷，是吗？
17．She must be playing basketball，isn't she？
她一定在打篮球，是吗？
选择下列各句的正确答案。
1．Hurry up，our teacher _____for us at the school gate．
A．must be waiting
B．must wait
C．might waiting
D．can be waiting
2．She doesn't answer the doorbell，she _____ be asleep．
A．might to
B．might
C．must have
D．should
3．"What has happened to George ？""I don't know，he _____ lost．"
A．can have got
B．may have got
C．might get
D．could get
4．Mr Li _____ be in Beijing because I saw him in town only a few minutes ago．
A．needn't
B．can't
C．shouldn't
D．mustn't
5．We can't blame John for the mistake．He wasn't here when we decided what to do．So_____ he about the plan．
A．wasn't
B．was known
C．can't be known
D．couldn't have known
6．My ballpen is nowhere to be found，I _____ while I was playing football．
A．must drop it
B．should have dropped it
C．must have dropped it
D．had dropped
7．It _____ be Li Ming who took my dictionary away．It be Zhang Hua who did it．
A．can't；must
B．mustn't；must
C．needn't；can
D．may not；can
8．The streets are all wet；It _____ rained heavily last night．
A．should
B．should have
C．must
D．must have
9．Tom must have learned Chinese for several years， _____he？
A．mustn't
B．hasn't
C．didn't
D．don't
10．Mr Wang must be at home now， _____he？
A．mustn't
B．doesn't
C．isn't
D．wasn't
11．She must have left for Shanghai， _____she？
A．mustn't
B．hasn't
C．didn't
D．doesn't
Key：1．A2．B3．B4．B5．D6．C7．A 8．D 9．B 10．C 11．C
- 考试辅导
