专四语法考点详解-情态动词

考点详解

Modal Verbs

情态动词

情态动词

表示说话的语气或情态。情态动词本身有词义，但不完全， 不能单独作谓语， 必须和动词一起构成谓语。

情态动词没有人称和数的变化。

大多数情态动词有过去式。

主要情态动词

Can

May

Will

Must

Shall

Need

Dare

Had better

Would sooner

Would as soon

Could

Might

Would

Have to

Should

Ought to

Used to

Would rather

might as well

情态动词问题解析:

may be & maybe

May be （可能是）--- maybe （或许）（副词） The news may be true.

Maybe the news is true.

考点详解

She may be waiting for you at home.

Maybe she is waiting for you at home.

May not & can not

may not 译为“可能不”、“也许不会”而非“不可以”。“不可以”为must not或can t（不许，不可以）。

---May I smoke here?

---No, you mustn t. /you can t /you can not.

The news may not be true.

You mustn t move any of the papers on the desk.

Can & be able to

Be able to 可以表示更多的时态。

We will be able to finish the work tomorrow.

He was not able to realize his greatest ambition.

Are you able to design a new computer program?

She has not been able to work out the complex problem.

ought to的否定式

ought to的否定式是ought not to，疑问句只把ought提前。 You ought to be responsible for yourself.

We ought not to look down on disabled people.

Ought we to count on him for the settlement of the debate?

Must

Must do

Must be

Must have done

Must 的反意疑问句

I must get up at six, ___？

She must be in the classroom now, _____?

They must have had great trouble trying to get there, ____?

用 must 提问时的回答

肯定回答：must

否定回答：needn t或don t /doesn t have to

考点详解

Must I come as early as 6 tomorrow morning?

Yes, you must.

No, you needn t. / No, you don t have to.

Mustn t & Needn t

Must he arrive very early?

No, he doesn t have to / No, he needn t.

Must & have to

Must: 主观上认为“必须” 作某事。

Have to: 受客观情况迫使而“不得不” 作某事

You must work harder now if you want to find a satisfactory job after graduation.

Children in remote areas have to quit school simply because their parents cannot afford their education. I must help him. {obligation, responsibility}

I have to help him. {unwillingness)

Must & have to的否定

否定must 表示“禁止，不允许，一定不要”

否定don t have to 表示“不必,不一定非得,不一定要” We mustn’t put off the trip no matter what happens.

We don’t have to put off the trip, although it rains.

Must & have to时态的区别

Must只用于现在 , 而have to则可用于不同时态。用had to表示过去 , 用will have to表示将来。

We had to resort to force in that case.

We will have to reconsider the whole thing if this plan fails. One must have faith in life.

have to

考点详解

have to的疑问句和否定句都要用助动词do/does，过去式则用did。

Do we have to wait for him to start dinner?

Does he have to show you the tickets to enter the cinema? Did I have to do the other task as well?

You don t have to come in person.

She doesn t have to bring her dictionary.

We didn t have to make preparations for the quiz.

Need & dare

Need & dare 既能作实义动词，又能作情态动词。

Need & dare在肯定句中，通常为实义动词，后面的不定式要带to，单数第三人称加s，有时态变化。

Need & dare作情态动词时，多用于否定句和疑问句。

Examples

She needs to work even harder if she wants to succeed in her study.

He dares to speak the truth.

Do you need to take a break?

They didn t dare to disobey.

Need he leave so soon?

You needn t have done all the heavy work.

She dare not go home late at night.

How dare you say I am unfair?

might as well

might as well译为“不妨”表示规劝。

You might as well wait to see what I can do for you.

You might as well leave now.

We might as well try a second time to see what s wrong with the equipment.

be to 可视为情态动词

be to的三种意义

①系表结构

考点详解

My duty is instruct students on what is wrong and what is right. ②将来时的特殊表达法

I was to go back home when the phone called.

③“应当”“规定是”可视为情态动词 –be supposed to You are to obey the school rules and regulations.

Would rather

表意愿：I would rather/sooner not go there on my own. 表选择：She would rather die than surrender to the enemy. （句型Would rather do sth. than do sth. else）

表虚拟：would rather sb. did /didn t do sth.

I would rather you didn t do anything for the time being.

Used to & would

情态动词used to表“过去常常做”。往往含有“不再如此”之意。 Would只能表示动作，不能表示状态。而used to都可以。 . He would ask the teacher some strange questions.

He used to ask the teacher ……

He used to be much better off than he is now.

He would be much …… (

More Information

Would侧重叙述过去, 而used to 强调过去和现在的对比。 Sometimes she would give me some pleasant surprises.

My mother used to be hot-tempered, but now she is very mild.

情态动词的完成式

needn t have done

表示过去本不必做的事情

You needn t have done all the calculation by yourself. We have computers to do that sort of work.

She needn t have risen so early. There was no hurry.

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