1. Look! The light is out in her room. She————to bed already.
A. must go
B. had to go
C.must have gone
D.has gone
2. ─There were already five people in the car but they managed to take me as well.─ It______ a comfortable journey.
A. can“t be
B. shouldn“t be
C. mustn“t have been
D. couldn“t have been
3. My sister met him at the Grand Theatre yesterday afternoon, so he ___ your lecture.A. couldn“t have attendedB. needn“t have attended
C. mustn“t have attended
D. shouldn“t have attended
4. You ______ be tired - you“ve only been working for an hour.
A. must not
B. won“ t
C. can“ t
D. may not
5. - Isn“ t that Ann“s husband over there?
- No, it _______ be him -I“m sure he doesn“t wear glasses.
A. can“t
B.must not
C. won“t
D. may not
6. I was on the highway when this car went past followed by a police car. They______ at lease 150 km an hour.
A. should have been doing
B. must have been doing
C. could have done
D. would have done
7. He _____ have completed his w ork; otherwise, he wouldn’t be enjoying himself bythe seaside.
A. should
B. must
C. wouldn’t
D. can’t
8. This cake is very sweet. You __________ a lot of sugar in it.
A．should putB．could have putC．might putD．must have put
9.—Tom is never late for work. Why is he absent today?
—Something ________ to him.
A．must happenB．should have happened
C．could have happenedD．must have happened
情态动词must,can,could,may,might表推测的用法
情态动词中的must, can, could, may, might都表推测。
其中must的可能性最大，can / could次之，may / might最小。
详尽用法如下：
1.must的用法
（1）表示推测“可能性”时，意思是“一定、准是”，语气较肯定，较有把握He must be American. = It is certain that he is American.他准是个美国人。
（2）must表推测只能用于肯定句。
如果要表示“一定不、肯定不”的意思时，应用can`t,如询问某种可能时，应用can。
He must know my address.他肯定知道我的地址。
（一定）
He can`t know my address.他肯定不知道我的地址。
（一定不）
Can he know my address?他知道我的地址吗？（询问可能性）
（3）must表示推测时，可以推测现在/正在发生的动作/过去发生的动作。
He must have a car now.（现在）他一定有辆小汽车。
He must be doing his exercises in the classroom.（正在进行）他一定在教室里做练习。
He must have finished the work.（过去发生）他一定已完成了工作。
注：must表示推测时很少用于将来的情况。
大凡不用He must come tomorrow.可用It`s certain / I`m sure that he will come tomorrow.
（4）在反意疑问句中，当附属部分含有表示推测意义的must时，疑问部分的助动词应与must后面的动词在非推测情况下的用法保持一致。
He must be a worker, isn`t he?（现在）他准时个工人，是吗？
It must have rained last night, didn`t it?（过去）昨晚一定下雨了，是不是？
You must have learned English for many years, haven`t you?（完成时）你一定学了好多年英语，是吗？
2.can / could的用法
（1）can表示推测“可能性”时，往往用于否定句或疑问句。
Can`t“一定不”，语气很肯定。
can在疑问句中意思是“会、可能”。
He can`t be at home. = It is impossible that he is at home.他一定不在家。
（2）can /can`t后可接进行时/完成时，表示对现在发生的动作或过去发生的动作进行推测。
They can`t be reading in the library.他们一定不在图书馆读书。
He can`t have gone to Shanghai for I saw him a minute ago.
他不可能去了上海，我刚才还看见他。
It`s so late. Where can she have gone?天晚了，她可能去哪儿了呢？（3）在反意疑问句中，当陈述部分含有表示推测意义的can`t时，疑问部分的助动词应与can`t后面的动词在非推测情况下的用法保持一致.
He can`t be a teacher, is he?他不是教师，是吗？
She can`t have finished her homework, has she?
她一定没有完成家庭作业，是不是？
（4）could可用于表示某事有可能发生或可能是事实。
Don`t eat it. It could be poisonous.不要吃它，可能有毒。
The plane could be delayed by fog.飞机可能会因为雾晚点。
（5）could还可以用于表示客气、婉转、礼貌的请求语气。
Excuse me, could you tell me the way to the bus station?
Could you help me?
（6）couldn`t表示否定推测，表示某事不可能真实，或由于特定事实或环境某事肯定不会发生。
It couldn`t possibly be poison.这不可能是毒药。
注：有时与形容词的比较级连用强调某人或某物不可能再更多地具有某种属性You couldn`t be more wrong.你真是大错特错。
I couldn`t be happier.我简直是美满极了。
3.may和might的用法
（1）may, might表示推测“可能性”时，意思是“可能”、“也许”，语气没有must肯定。
He may / might be American. = It is possible that he is American.他可能是个美国人。
注：might不表示过去时态，只是语气上比may更婉转，表示的可能性更小。
（2）may, might表推测时，可以用于否定句，意思是“可能不、也许不”，但不用于疑问句。
He may / might not be at home.他也许不在家。
（3）may, might可以推测现在正在发生的动作或过去发生的动作。
He may / might be sleeping now.（现在）他可能正在睡觉。
The boy may / might not be watching TV at home.（现在）
这个男孩可能没在家看电视
These students may / might have seen the film before.（过去）这些学生以前可能看过这部电影。
（4）may, might还可以推测将来的情况。
I think we should take raincoat with us, it may rain.
我想我们应该带上雨衣，可能要下雨了。
She might not come this afternoon.她今天下午可能不来。