must　　　　 用于肯定句

can　 　　用于否定句或疑问句

May　　用于肯定句或否定句　　

should 　用于肯定句

问句　　肯定回答　　否定回答

Need you…?Yes, I must.　No,I needn‘t

Must you…?Yes, I must.　　 No, I needn’t./don’t have to.

May I …?　　 Yes, of course.　 No, you mustn’t.

Could you…? Yes, you can.　 No, you can’t.

12.had better表示"最好"

had better 相当于一个助动词，它只有一种形式，它后面要跟动词原形。had better do sth　 .had better not do It is pretty cold. You'd better put on my coat.

She'd better not play with the dog.

had better have done sth表示与事实相反的结果，意为"本来最好"。

You had better have come earlier.

11.should 和ought to 都为“应该”的意思，可用于各种人称。

---Ought he to go?

---Yes. I think he ought to.

表示要求，命令时，语气由 should(应该)、had better最好)、must(必须)渐强。

10.need&dare

这两词既可做实义动词用，又可做情态动词用。作为情态动词，两者都只能用于疑问句，否定句和条件句。 need 作实义动词时后面的不定式必须带to，而dare作实义动词用时, 后面的to 时常可以被省略。

1)　　　 实义动词:need+ n. / to do sth

2)　　　 情态动词： need，只用原形need后加do，否定形式为need not。

e.g.　 a. ----Need you go yet?　　　　　

----Yes, I must.

----No, I needn't.

3) 　need 的被动含义：need, want, require, worth(形容词)后面接doing也可以表示被动：　

need doing = need to be done

9. have to＆must

1)　两词都是'必须'的意思，have to 表示客观的需要， must 表示说话人主观上的看法，既主观上的必要。

e.g. 　a. My brother was very ill, so I had to call the doctor in the middle of the night. (客观上需要做这件事)　　

　b. He said that they must work hard. (主观上要做)

2)　have to有人称、数、时态的变化，而must只有一种形式。但must 可用于间接引语中表示过去的必要或义务。

e.g. 　a. He had to look after his sister yesterday.

3) 在否定结构中： don’t have to　 表示“不必”　 mustn’t　表示 “禁止”

e.g. 　a. You don‘t have to tell him about it.　　

　　　 b. You mustn‘t tell him about it.　　

8. shall, should 表示命令, 警告, 允诺, 征求, 劝告, 建议, 惊奇。

　shall的用法

用于第一,第三人称征求对方的意愿

e.g. 　a. What shall I wear on the journey?　　　

　　 b. When shall he be able to leave the hospital?

should 的用法

1)用于第一人称疑问句中询问对方的意愿，但语气较委婉温和

e.g. a. What should we do now? 我们现在该怎么办？

2)表示应该、必须，常与must 换用。

e.g. a. We should (must) master a foreign language at least.

3).should 表示劝告，建议，命令，此时也可用ought to. 在疑问句中，通常用should代替 ought to.

4) should have done 表示过去应该做　　 而实际没有做　should not have done 表示过去不该做而实际做了．

7. will (would) 表决心、愿望。 would 为 will 的过去式, 可用于各人称。

　1)will表示经常性、习惯性、倾向性，would表示过去的习惯行为。

e.g. 　a. He will sit there hour after hour looking at the traffic go by.　

　b.He would come to see me when he was in Beijing.

　2)表示意志，决心或愿望。

　e.g. 　a. Surely we will support all the people in the world in their struggle for peace. 　　　 b. He would not let me try it .

　3)表示对对方的请求，用于第二人称作主语的疑问句中，would的语气比will委碗,疑问句中一般用some, 而不是any。

e.g. 　a. would/will you kindly tell me the way to the station? b. Would you like some cake?

4)would like　　　 =　　 want to 想要　

　 Would like to do　 =　 　want to 想要　

e. g. 　a　 Would you like to go with me?

6. ought “应当；应该”，后面跟带有 to 的动词不定式。

　 You ought to read these books if you want to know how to repair the motorcar.　 如果你想知道如何修理汽车,你应该读这些书。

　 You ought to bring the child here.　 你应该把孩子带来。

ought + to have done 句型。指过去动作,表示一件事情该做而未做。

　 You ought to have been here yesterday. 你昨天就应该来。

ought not to have done 句型。表示一件不该做的事情却做了。

　 You ought not to have taken the book out of the reading-room.　

　 你不应该把书带出阅览室。

5. dare “敢”，多用在否定或疑问句中。

　The little girl dare not speak in public.　 小女孩不敢在公众面前说话。

　Dare you catch the little cat?　 你敢抓小猫吗?

　　　　 dare 除用作情态动词外，更多的是当实义动词使用， 用法同实义动词一样，要考虑人称，单复数，时态等。

　Do you dare to walk in the dark?　 你敢黑夜走路吗？

　He doesn't dare to tell the teacher what happened that day.　 他不敢告诉老师那天发生的事。