1. Unit 15
Grammar

2. Use some modal verbs to say sth. that is possible.
FORMS 肯定形式 否定形式 疑问形式 备注
MUST
CAN
MIGHT
must / /
can can’t/cannot Can···？
COULD
could could not Could···？
MAY
may may not
might might not

3. ORDER:
Might May Could Can Must
UNCERTAIN CERTAIN

4. Mum: Who is it?
Jim: (一定是Tom。)
It must be Tom.
(可能是Kate。)
It may be Kate.
(绝对不是Marry。)
It can’t be Marry
(可能不是Tommy。)
It couldn’t be Tommy.

5. Modal Verbs (3) must can / could may / might
When you are very sure of something, you use must in positive sentence and cannot or can’t in negative sentences.
When you are quite sure about something, you use can.
When you think that something is possible, but you are not very sure, you use could, may or might.

6. must的用法 We must have been met somewhere before.
It must be nice to take a walk here, __________?
isn’t it
2. It must have rained last night, _________?
didn’t it
2. Must have done 意为“一定做过”，表示对过去发生的事情进行肯定推测。如：
1. 我们以前一定在哪里见过面。
We must have been met somewhere before.
2. 你昨天一定看到她了，对不？
You must have seen her yesterday, didn’t you?

7. can / could 的用法 You can’t be serious, are you?
can / could表示的可能性比must小，can表现在和将来，could既可表过去，也可表现在或将来，但它的可能性给can的小。
can / could可与not连用，表示否定推测，也可用于疑问句中.
Can / could表推测时，其反间疑句也是根据动词的实际时态国以变化。如：你不可能当真的，对不地？
You can’t be serious, are you?
4. can / could have done，意为“本来能够”，用于否定句时，意为“过去（不）可能”，而实际上都未发生。
如： 你本来可以来早点的。
You could have come earlier.

8. may/might的用法 May I leave now? The teacher may not e serious.
May / might可与not连用，表示否定推测，但may用于疑问句时中能表示请求允许。
The teacher may not e serious.
May I leave now?
3. May / might have done, 表示对过去可能发生某事的推测。
如： 你在做这件事时也许注意到了什么。
You may have noticed something while you were doing this.

9. 对过去事情的推测： 可能已经做过某事 May have done 也许已经做过某事 Might have done 本来可以做某事
本来应该做某事
本来不应该做某事
不可能已经做过某事
May have done
Might have done
Could have done
Can have done
Should have done
Ought to have done
Shouldn’t have done
Can’t have done
Couldn’t have done

10. 1.I may have been pretty in those days.
2. He can’t have been to Beijing.
3.She might have been hurt at the party yesterday.
4. You should have helped him.
5. I could have finished my homework,but your radio was too noisy.
6. You shouldn’t have quarreled with him.
7. You ought to have been here five minutes earlier.

11. I am not sure whether he will come or not. He must come tonight.
He mustn’t be an American because he can’t speak English at all.
I tried to call him at the office, but there is no reply. He can be at home.
--- Is John coming by train?
--- He should, but he ____ not. He likes driving his car. (NMET 2002)
a. must b. can c. need d. may
5. A left luggage office is a place where bags ____ be left for a short time, especially at a railway station
a. should b. can c. must d. will

12. 6. My English-Chinese dictionary has disappeared
6. My English-Chinese dictionary has disappeared. Who ____ have taken it?
a. should b. must c. could d. would
7. My sister met him at the Grand Theater yesterday afternoon, so he ______ lecture.
a. Couldn’t have attended
b. needn’t have attended
c. mustn’t have attended
d. shouldn’t have attended
Could I borrow your dictionary?
---- Yes, of course you ____. (NMET1992)
a. might b. will c. can d. should

13. Don’t be late again. You ____ be here on time.
A. may B. can C. must D. needn’t
You ___ do it even if you don’t want to.
A. can’t B. mustn’t C. needn’t D. have to
3. —— Must I take a bus?
—— No, you ___. You can walk from here.
A. mustn’t B. don’t
C. don ‘t have to D. had better not to
4. —— It is rather cold here. Shall we light a fire?
—— No, we ___, because things here are easy to catch fire.
A. won’t B. can’t C. mustn’t D. needn’t

14. 5. Mr. Bush is on time for everything
5. Mr. Bush is on time for everything. How_______ it be that he was late for the opening ceremony? A. can B. should C. may D. must My sister met him at the Drand Theatre yesterday afternoon, so he _______ your lecture A. couldn’t have attended B. needn’t have attended C. mustn’t have attended D. shouldn’t have attened There was a lot of fun at yesterday’s party. You _____ come, but why didn’t you? A. must have B. should C. need have D. ought to have Jack______ yet, otherwise he would have telephoned me A. mustn’t have arrived B. shouldn’t have arrived C. can’t have arrived D. needn’t have arrived

15. 9. Sir, you_____be sitting in the waiting room
9. Sir, you_____be sitting in the waiting room. It is for women and children only A. oughtn’t to B. can’t C. won’t D. needn’t Sorry, I’m late. I______have turned off the alarm clock and gone back to sleep again A. must B. should C. can D. will Are you coming to Jeff’s party? I’m not sure. I _______ go to the concert instead A. must B. would C. should D. might Michael ________be a policeman, for he is much too short A needn’t B. can’t C. should D. may 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

16. Grammar Exercise One He can’t be at home. / He must be out.
2) They must earn a lot of money.
3) They must be poor. / They can’t be very rich.
4) He must be terribly busy.
5) It must be very interesting.
Exercise Two
must/may be 2) must be 3) must/may be
4) can’t be ) must/may be