必修三Unit1 情态动词学案

必修三Unit1

语法专题课情态动词

一、can和could

1．表能力

The girl can dance very well.

He can speak French

区别：be able to也可表达能力，但常用来表达在某件事情中所表现出来的能

力，尤指克服困难能够完成某事。= manage to do /succeed in doing

The fire spread through the hotel very quickly, but everyone was able to get out.

2. 在口语中, 可以表示请求或允许：

. Can I sit here?

Could you lend me some money?

could可以代替can表示请求, 但语气较can客气、委婉，could 提问，答语

用can

—Could I borrow your pen?

—Yes, you can./ No, I am afraid not.

3. 用在肯定句中。can用于肯定句中表示一种理论上的可能性，意为“有时候

会…”，

Anybody can make mistakes.

The spring in Kunming can be quite cold.

4．can, could表达推测时，一般用于疑问句和否定句中。

can(could) + have + 过去分词”的疑问或否定形式表示对过去发生的行为怀疑

或不肯定。如：

Today is Sunday. He can’t be at school.

Who can it be?

. Can he have got the book?

He cannot have gone to that town, for I saw him just now

5. could have done本来能够做某事但未做。(表虚拟，用于肯定句)

If you followed my advice, you could have finished it.

I could have worked out the problem, but I was too nervous.

6. cannot…. too 越…越…; 怎么做不为过

You cannot be too careful.

二、may和might

1. 表示请求、允许（比can正式）：You may go now.

May I watch TV after supper?

= Yes, you may.

= No, you mustn’t.

2.表示祝愿,位于句首May you succeed! May you be lucky!

May you have a good journey!

May you live long !

3.may (might) as well = had better do (最好做某事）

You’d better take notes carefully.

You may as well take notes carefully

4．“may(might) + have + 过去分词”表示对过去发生的行为的推测。

He may not have finished the work.

What a pity! Considering his ability and experience, he might have done

better.

三、must 和have to

1．must表主观“必须have to 表客观“不得不”

I must go home this Saturday.

I’ve got a cold, so I have to see a doctor.

—Must I stay here?

—Yes, you must.

No, you needn’t. /you don’t have to.

★mustn’t表禁止，不准，一定不要。

You mustn't play with fire.

You mustn't take drugs.

2. 条件句或疑问句: 可以用来表示责备、抱怨的感情色彩，意思为“偏要，硬要”

1) —May I smoke here?

—If you must, choose a seat in the smoking section.

2) John, look at the time. Must you play the piano at such a late hour?

3）—How much do you earn?

—I’ll tell you if you must know it.

3. must be表示推测，意为“一定是……”只用于肯定、

must have done意为“一定做过某事或某事肯定发生了”并且有前文铺垫

Listen! There must be some children in the room.

The road is wet. It must have rained last night.

四、will和would

1. 表意愿或意志

I will never do it again.

If you will marry me, whatever I have is yours, and mine is yours.

2. 提出请求或建议,在疑问句中用于第二人称。

If you want help, let me know, will you?

Will you type this, please?

★祈使句问句与答语一般用will

Open the door, will you?

—Please come to my party.

—Yes, I will

3. 表示习惯和倾向性:will表示现在的习惯，would表示过去的习惯。

Oil will float on water.

This window won’t open.

When he was a child, he would often go skiing.

4.would & used to (过去常常，习惯于）

would 现在有可能做，也有可能不做，used to 现在一定没有做

There used to be a big tree.

I would go to the library when I was free.

五shall和should

1. shall用于第一、第三人称疑问句中，表示说话人征求对方的意见或向对

方请示。

Shall we go by train, Mom?

Shal l he attend the meeting?

When shall he be able to leave the hospital?

2． Shall用于第二、第三人称，表示说话人给对方命令、警告、允诺或威胁。如：