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Unit2 grammar and usage

Modal verbs

1.Ability

(1)He can run the 100m sprint in 11 seconds.

(2)Can the girl read before she goes to school?

ought to/should

1.表示义务，“应该”，用于各种人称

You should be polite to your teacher.

You shouldn’t spend so much time playing

computer games.

2.表示推测，“想必，估计”的意思．

If they start today, they should arrive there in two days.

3.表示与想象的不一样”照说应该……”

I wonder where Mary is. she should be here now.

4.在某些从句中，表示虚拟语气．

He suggested that I (should) go to shanghai tomorrow.

He demanded that we (should) solve the problem at once.

5.表示惊讶，忧虑，惋惜等感情色彩．

I am surprised he should eat so little every day.

Have to/must

have to 表示客观需求

must 表示主观愿望

Everyone has to go to school at the age of 7 in the country.

We must wok hard to make our country strong and rich.

You must work hard to win the gold medal.

Certainty might/may/could/should/ought to/will /must

She might win a medal at the Olympics.

She may be at home now.

She could read and write at the age of 4.

She should come to join us.

She ought to/will /must help me whenever I am in trouble.

Permission can /could/may/might

A: Can I watch the Olympics ?

B: Yes, you can.? No, you can’t.

A: May I have a look at you photo?

B: Yes, you may./ No, you mustn’t.

No, you’d better not.

Could比can 更委婉，might比may 更委婉

Make requests

Will; can; could; would

A: Can/Will /Could/Would you help me with my training?

B: Yes, I can/will/can/will.

Make suggestions

Shall we/I /He/She/They do some exercise

this morning?

Shall常用于第一，三人称，表示征求对方意见

A: Shall he come in? B: Ok.

Make offers

I’ll wash your sports jacket.

Shall I get a ticket for you?

Shall we carry the books for you ?

Shall I clean the blackboard for you?

give advice

You should not/ought not to eat a lot before swimming.

The students should spend all their time working at their lessons.

We should not laugh at those who are in trouble.

和其他时态的连用

The boys may be playing football on the playground.

The boys may have finished their homework by the time school is over.

He plays basketball very well. He must have practiced it a lot.

Our headmaster must have been to USA, for he knows the country so much.

must have done 的反意疑问句

You must have seen the film, haven’t you?

You must have seen the film last week, didn’t you?

His parents must have beaten him, haven’t they?

His parents must have beaten him yesterday, didn’t they?

can / be able to

can 的形式只有can ;could两种

be able to 的形式有am/is/are able to; was/were able to; have/has been able to等多种

Can 一般能力

Be able to 经过努力后而达到的一定境界

My brother can play table tennis.

My brother is able to dive under water for 10 minutes.

shall will

Shall表达诺言;will表示决心或决定

Don’t worry. You shall have the tickets for the games.

Liu Mei will go and buy the tickets for the games.

Shall +一，三人称？Will+二，三人称？

1. Shall we go swimming this weekend?

2. A group of students are waiting to see you outside. Shall they come in?

3. Will you go hiking with me in the mountains?

4. Will he pay for me ?

mustn’t needn’t

mustn’t “不准，不许”　语气强烈

needn’t “不需要，没必要”　语气缓和

You mustn’t miss this football match. It’s very important.

You needn’t watch the game if you don’t want to.

Must we clean the classroom? Yes, you must. /No, you needn’t.

need dare

作为情态动词时，两个词常用于疑问句和否定句；用作实义动词时，可用于各种句式．

情态动词时：

---Need I help you? ---Yes, please.

You needn’t telephone him now.

How dare you talk to the teacher like that?

The girl dare not go out alone at night.

用作实义动词时

We need to tell him the news.

You don’t need to tell him the news.

Do the flowers need watering?

I didn’t dare to tell you the truth.

Would you dare to catch the snake with your hand?

The boy dares to do anything he likes.