情态动词的用法分类

二：情态动词

情态动词表推测和可能性的用法，情态动词+ have done，的用法，shall, should, can和must 表示特定语气的用法应是考查的热点。

1）情态动词+have done

Must+ have done表示对过去情况的推测，只有于肯定句，意思是“一定……”。其否否定式则表示“本来不该做而实际上做了”，常有责备的语气。

Could+ have done表示“本来有能力做而实际没做”。

Needn’t+ have done表示“本来不必做，实际上做了”。

May/might+ have done表示对过去情况的推测，多用于陈述语气，意思是“可能……”

用might比may更加委婉。

2）Shall的用法

①用shall表示“意愿”“意愿”即愿意做某事,一般适用于第二，三人称主语，这时所表达的“意愿”不是主语（听话人）的“意愿”而是说话人的“意愿”

You shall stay with us as long as you like.

=I’m willing to let you stay with us as long as.

He shall be praised if he works hard for the people.

=I’ll see that he is praised

②shall 表达“意图”即打算,用于疑问句中（shall I /we……?）是征询听话人的意见或意图

Shall I carry the suitcase for you?

=Do you want he to carry your suitcase?

Shall we have dinner?

=Let’s have dinner, shall we?

=Do you agree with my intention to have dinner.

③shall表示“决心”即坚持做某事,主要用于第二，三人称的主语，表示说话人的强烈意志和决心。

You shall obey my orders.

=I insist that you obey my orders.

He shall leave the country at once.

=I insist that he leave the country at once .

They shall do what I told them to .

=I ’m determined to make them do it.

④作这一用法的否定形式，shall not/shan’t 表示说话人“禁止”或“威胁”

You shan’t get away with it.

=I will never allow you to get away with it.

You shall not have it ,It’s mine.

=I don’t allow you to have it.

No one shall stop me.

=I don’t allow anybody to stop me.

Foreign countries shall not interfere in our internal affairs.

=We are determined not to allow any foreign country to interfere in our internal affairs.

3) should 的用法

Should:可用在某些语境中表达惋惜，忧虑，欢乐，惊讶等感情色彩，例如在某些that分句中。

It’s pity that he should leave so soon.(惋惜)

They were sorely distressed that their motherland should be in such great danger. (忧虑)

It’s unbelievable that he should be working so hard.(惊讶)

4）must的用法

must“必须”must的否定有两种must not/mustn’t意思是“不许”“禁止”相对比should “应该”should not/shouldn’t意思是“不应该”must not/mustn’t的语气更加强烈，这就意味着说话人是权威的一方，对人对己都适用。

You mustn’t talk like that

5）can的用法

①表示“能力”=be able to

Yes! I can do it .

I can help you.

②表示“可能”，较多地用于否定句和疑问句，而could则不受词限

Can/Could the news be true?

Where can he be?

-he may be in the office.

Can they have missed the bus?

-yes , they may have.