董桂萍

一、must

1.表義務(wù)，“必須”（主觀）

Eg. You must finish the job today.

2. 否定形式mustnt表”不許、禁止”

Eg: You mustnt leave here.

3. 表推測(cè)，可能性大，且用于肯定句中，“一定”（否定句用cant ，“一定不”）

eg. He must be ill. He looks so pale.

Eg. It cant be him, because he is ill and in hospital today.

4. 表 “偏偏，非要”

Eg. Its freezing cold. Must you go outside playing with snow？

5. must問(wèn)句的回答

—Must I clean the dining room at once？

— Yes, you must.

No， you neednt. / you dont have to.

二、have to

1. have to表客觀的需要和義務(wù)，“不得不，必須”

2. have to 有人稱、數(shù)的變化： has/have/had to

3. 否定：dont have to=neednt“不必”

三、 can，could

1. 表能力，“能”“會(huì)”“能夠”

Eg. —Can you drive a car？— Yes， I can. / No， I cant.

2. 表允許，許可，在口語(yǔ)中代替 may， “可以”

Eg. Can I use your bike？

此時(shí)過(guò)去式could表示的語(yǔ)氣更加委婉、客氣，但回答只能用can

Eg.— Could I come to see you tomorrow？

— Yes, you can.

3. 表推測(cè)（客觀可能性）或驚異，懷疑，不相信，常用于否定句，疑問(wèn)句和感嘆句中

Eg. Today is Sunday. He cant be at school.

How can he be so careless！

四、may，might

1.表許可或征求對(duì)方的許可， “可以” （口語(yǔ)中可用can替代）

Eg.You may go now.May I use your computer？

問(wèn)句中過(guò)去式might表示的語(yǔ)氣更加委婉、客氣

Eg.Might I use your pen for a while？

2.表推測(cè)， “或許，可能”，通常只用于肯定句（疑問(wèn)句中用can），且might比may的可能性小

Eg.The story may be true. Can the story be true？

3. 以may開頭的疑問(wèn)句回答

—May I smoke here？

— Yes， you may/can. 或Yes， please.

— No， you cant. 或No， you mustnt.（禁止） 或No， youd better not.（客氣）

注意：— Can it be true？

— Yes, it may be.（可能）/might be（可能性更?。?或Yes， it must be.（肯定）

— No， it cant be true.（不可能） 或No， it may not be true.（可能不）

4. 表祝愿 May+主+v.原 （區(qū)：Wish+主+n. /adj.）

Eg.May you be happy. Wish you happy.

5. may/might as well最好，倒不如

Eg. You may as well do it at once.

五、shall

1.第一、三人稱疑問(wèn)句中表請(qǐng)求或征求對(duì)方意見

2.第二、三人稱陳述句中表命令，警告， 決心，允諾， 威脅

體會(huì)下列例句：

Shall she come right now？

Nothing shall stop us from carrying out the plan.

You shall get a MP5 if you are admitted to the key middle school.

You shall do as your father says.

He shall be punished if he disobeys.

六、情態(tài)動(dòng)詞+have done

1. must have done表對(duì)過(guò)去發(fā)生事情的肯定推測(cè)，“過(guò)去一定……” 其否定形式為：cant/couldnt have done “過(guò)去一定沒有……”

Eg. The ground is wet. It must have rained last night.

He couldnt have gone to Beijing， for I had a talk with him just now.

2. could have done 表本可以做某事而事實(shí)上沒做（不用can）

Eg. The girl could have been saved.

3. might have done 表可能做過(guò)（了）某事

Eg. She might have gone to Shanghai.

4.should have done 表過(guò)去本應(yīng)該做某事卻沒做

shouldnt have done 表過(guò)去本不應(yīng)做某事卻做了

Eg. You should have set off earlier.

You shouldnt have helped him, he could do it himself.

5. neednt have done 表過(guò)去本不必做某事卻做了

Eg. You neednt have waited for me.

（作者單位山西省孝義市第三中學(xué)）

?誗編輯 孫靈娟