must　　　　 用于肯定句

can　 　　用于否定句或疑問(wèn)句

May　　用于肯定句或否定句　　

should 　用于肯定句

問(wèn)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 相當(dāng)于一個(gè)助動(dòng)詞，它只有一種形式，它后面要跟動(dòng)詞原形。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表示與事實(shí)相反的結(jié)果，意為"本來(lái)最好"。

You had better have come earlier.

11.should 和ought to 都為“應(yīng)該”的意思，可用于各種人稱(chēng)。

---Ought he to go?

---Yes. I think he ought to.

表示要求，命令時(shí)，語(yǔ)氣由 should(應(yīng)該)、had better最好)、must(必須)漸強(qiáng)。

10.need&dare

這兩詞既可做實(shí)義動(dòng)詞用，又可做情態(tài)動(dòng)詞用。作為情態(tài)動(dòng)詞，兩者都只能用于疑問(wèn)句，否定句和條件句。 need 作實(shí)義動(dòng)詞時(shí)后面的不定式必須帶to，而dare作實(shí)義動(dòng)詞用時(shí), 后面的to 時(shí)常可以被省略。

1)　　　 實(shí)義動(dòng)詞:need+ n. / to do sth

2)　　　 情態(tài)動(dòng)詞： need，只用原形need后加do，否定形式為need not。

e.g.　 a. ----Need you go yet?　　　　　

----Yes, I must.

----No, I needn't.

3) 　need 的被動(dòng)含義：need, want, require, worth(形容詞)后面接doing也可以表示被動(dòng)：　

need doing = need to be done

9. have to＆must

1)　兩詞都是'必須'的意思，have to 表示客觀的需要， must 表示說(shuō)話人主觀上的看法，既主觀上的必要。

e.g. 　a. My brother was very ill, so I had to call the doctor in the middle of the night. (客觀上需要做這件事)　　

　b. He said that they must work hard. (主觀上要做)

2)　have to有人稱(chēng)、數(shù)、時(shí)態(tài)的變化，而must只有一種形式。但must 可用于間接引語(yǔ)中表示過(guò)去的必要或義務(wù)。

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

3) 在否定結(jié)構(gòu)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, 允諾, 征求, 勸告, 建議, 驚奇。

　shall的用法

用于第一,第三人稱(chēng)征求對(duì)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)用于第一人稱(chēng)疑問(wèn)句中詢(xún)問(wèn)對(duì)方的意愿，但語(yǔ)氣較委婉溫和

e.g. a. What should we do now? 我們現(xiàn)在該怎么辦？

2)表示應(yīng)該、必須，常與must 換用。

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

3).should 表示勸告，建議，命令，此時(shí)也可用ought to. 在疑問(wèn)句中，通常用should代替 ought to.

4) should have done 表示過(guò)去應(yīng)該做　　 而實(shí)際沒(méi)有做　should not have done 表示過(guò)去不該做而實(shí)際做了．

7. will (would) 表決心、愿望。 would 為 will 的過(guò)去式, 可用于各人稱(chēng)。

　1)will表示經(jīng)常性、習(xí)慣性、傾向性，would表示過(guò)去的習(xí)慣行為。

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，決心或愿望。

　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)表示對(duì)對(duì)方的請(qǐng)求，用于第二人稱(chēng)作主語(yǔ)的疑問(wèn)句中，would的語(yǔ)氣比will委碗,疑問(wèn)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 “應(yīng)當(dāng)；應(yīng)該”，后面跟帶有 to 的動(dòng)詞不定式。

　 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車(chē),你應(yīng)該讀這些書(shū)。

　 You ought to bring the child here.　 你應(yīng)該把孩子帶來(lái)。

ought + to have done 句型。指過(guò)去動(dòng)作,表示一件事情該做而未做。

　 You ought to have been here yesterday. 你昨天就應(yīng)該來(lái)。

ought not to have done 句型。表示一件不該做的事情卻做了。

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

　 你不應(yīng)該把書(shū)帶出閱覽室。

5. dare “敢”，多用在否定或疑問(wèn)句中。

　The little girl dare not speak in public.　 小女孩不敢在公眾面前說(shuō)話。

　Dare you catch the little cat?　 你敢抓小貓嗎?

　　　　 dare 除用作情態(tài)動(dòng)詞外，更多的是當(dāng)實(shí)義動(dòng)詞使用， 用法同實(shí)義動(dòng)詞一樣，要考慮人稱(chēng)，單復(fù)數(shù)，時(shí)態(tài)等。

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

　He doesn't dare to tell the teacher what happened that day.　 他不敢告訴老師那天發(fā)生的事。