• 情态动词除 ought 和 have 外 , 后面只能接不带 to 的不定式。

• 情态动词没有人称 , 数的变化 , 即情态动词第三人称单数不加 -s 。

• 情态动词没有非谓语形式 , 即没有不定式 , 分词等形式。

• 有的情态助动词有现在时和过去时两种形式。

• 有的有现在时而无过去时。

• 有的有过去时而无现在时。

现在时 过去时may might

can could

must (had to)

ought to --

will would

shall should

need --

dare dared

-- used to

e.g. Two eyes can see more than one.

I am so strong that I can lift this stone.

He said that Jack couldn’t finish his

work in such a short time.

Could you follow my step?

He is only four, but he is able to read.

She was able to do it without my help.

Will you be able to come to my party

tomorrow?

表能力表能力can

could

be able to 有时态变化有时态变化

You can go now.

I won’t let you down.

Could I say it in Chinese?

May I know your name?

Would you mind closing the door?

Shall we dance?

Might I have a word with you?

语气

强

弱

表许可 , 征询意见

can, will

could / may / would / shall / might

There must be a mistake.You may walk ten miles without seeing a house.He might get there on time.It can be true.In those days few workers could support their families.

表可能性( 猜测 )

must

may, might, can, could

肯定句

语气

强

弱

语气

强

弱She can’t be serious.

We couldn’t have done better.

People may not pick flowers in this garden.

She was afraid they might not like the idea.

表不可能( 猜测 )

can’t, couldn’t

may not, might not

否定句

mustn’t, shouldn’t

had better not

We mustn’t waste our time.

They shouldn’t left so soon.

You’d better not disturb him.

表禁止

You should do what your parents tell you.

If you can’t finish the book by then, you

must come and renew it.

This is a lovely party, but we have to go

because of the baby-sister.

The bridge was not wide enough so that

somebody had to give way.

should, must

have to表义务 ( 应

该 ) 有时态变化

Translate the following sentences.

1.Tom, you mustn’t leave all your clothes on the floor like this!

2. He must have completed his homework; otherwise, he couldn’t be enjoying himself by the seaside.

( 表示禁止 , 意为 “不许” )

(must + have + 过去分词 , 表示对过去事情肯定的推测 )

3. Helen may go on the trip with us,

but she isn’t quite sure yet.

4. --- Isn’t that Ann’s husband over

there?

--- No, it can’t be him—I’m sure

he doesn’t wear glasses.

( 表示可能性 , 意为 “可能” )

( 对目前状态表示否定推测 , 意为 “不可能” )

5. I often see lights in that empty house.

Do you think I should report it to the

police?

6. Children under 12 years old in that

country must be under adult

supervision when in a public library.

( 表示应该 )

表示义务或必要 , 意为 “必须”

7. ---Who is the girl standing over there?

--- Well, if you must know, her name is

Mabel.

8. ---I’ll tell Mary about her new job

tomorrow.

---You should have told her last

week.

表示主张 , 意为 “一定要”

表示与过去事实的相反 , 意为 “本应该……”

9. You can’t imagine that a well-

behaved gentleman should be so rude

to a lady.

10. The interest shall be divided into five

parts, according to the agreement

made by both sides.

表示吃惊 , 意为 “竟然会”

( 表示义务或规定 )

11. --- Is John coming by train?

--- He should, but he may not. He

likes driving his own car.

12. Since it is raining, we have to stay

indoors.

13. I must go now. There are a lot of

things I want to do.

( 表示对现在或将来的推测 )

( 表客观需求 )

( 强调主观意图 )

14. There must be some reason for his

absence.

15. --- Need I do the experiment again

after class?

--- Yes, you must. (No, you

needn’t/ don’t have to.)

( 表示对现在事情的推测 )

need 引起的疑问句肯定回答用 must.

1. —That must be a mistake.

—No, it _____ a mistake.

A. must not be 　 B. needn’t be 　 C. cannot be 　　 D. would not be

2. — _____ I water the trees on Tuesday?

— No, you needn’t.

A. Can B. Must C. May D. Shall

3. He _____ not pay unless he is punis

hed to pay.

A. shall 　 B. will C. can D. would

4. I _____ such a mistake again.

A. shall never make 　　 B. may never make 　　 C. can never do 　　 D. need never do

5. — _____ I turn on the radio?

— You’d better not. It is noisy enough

in this room.

A. Shall B. Must C. Need D. Do

6. Let’s go to the library this afternoon, _

____?

A. shall we 　　 B. will we 　　 C. can we 　　 D. should we

7. Where are my keys? I _____ lost them.

A. ought to 　　 B. should have 　　 C. will have 　　 D. must have

8. Even if he has time, he _____ shopping

in town on Sunday.

A. won’t go 　　 B. will go 　　 C. won’t go to 　 D. doesn’t go

9. He _____ finished earlier.

A. shall have 　　 B. ought to 　　 C. could have 　　 D. must have

10. In case I _____, I would try again.

A. will fail 　　 B. would miss 　　

C. should fail D. shall miss

11. Since the road is wet this morning, _____ last night.

A. it must rain 　　　　　　 B. it must have rained

C. it must be rained 　　　　 D. it must have been rained 12. He asked me if he _____ open the window.

A. shall B. would C. will D. should

13. Everyone _____ do his best to

make the world safe and clean.

A. can B. may C. should D. had to

14. _____ to have lunch with us today?

A. Do you like 　　 B. Would you like 　　 C. Will you like 　　 D. Have you like

15. — Will you lend me your book?

— Yes, I _____.

A. will B. need

C. can D. must

Correct the mistakes.

• John shoulds go to school on time.

• At that time we thought we musted hand in our paper.

• You must to finish your homework in time.

• We don’t can be there tomorrow.

• They should may do that.

should

must

can’t

should / may

Fill in the blanks.

must, can, may, ought to, have to, should

1. He _____ tell a lie, because he is an

honest boy.

2. The last bus has gone. We _______ take

a taxi.

3. Harry’s been driving all day — he

_____ be tired.must

have to

can’t

4. I knew things are hard with you, but

you _____________________ try to get

over the difficulties.

5. The girl _____ know the truth, but I

am not sure.

may

must / ought to / should

Finish the exercises 1-4

on page 44 and 91.