情态动词具有一定词义，不能单独作谓语，必须和动词原形连用一起构成谓语。用来表示愿望、态度或推测等。

一、情态动词的情态意义表示法

考点一：can可表示现在或将来的能力，意为“能；会”。can还可表示请求、允许，意为“可以”。

考点二：could 可表示过去的能力；当could 表示允许时，语气比can更加委婉和客气。couldn't意为“不能”。

考点三：may表示请求、允许，意为“可以”。

考点四：might表示允许时，语气比may更加委婉和客气。

考点五：must 表示义务、命令或必要，意为“必须”，强调主观看法。mustn't 表示“不允许；禁止”之意。

考点六：have to意为“不得不”，强调客观需要。

考点七：should 意为“应该”，既可以表示义务或责任，还可以表示劝告或建议。其否定式为 shouldn't，意为“不应该”。

考点八：had better do sth. 意为“最好做某事”，其否定式是在better后加not。

考点九：need表示“需要”，通常用于否定句或疑问句中。

【考例链接】

( )1. We need clean air and water, so we ______ protect the environment.

A. can B. may

C. must D. might

(2016辽宁大连)

( )2. —Hi, you ______walk on the grass.

—Sorry, I ______ do it again.

A. can't; will B. needn't; won't C. mustn't; won't

(2016黑龙江齐齐哈尔)

( )3. —I've bought all the food for the party tonight.

—Thank you. Then I ______ go to the supermarket.

A. can't B. mustn't

C. shouldn't D. needn't

(2016江苏常州)

二、情态动词的推测用法

(以下情态动词对可能性的推测排列顺序由强到弱)

【考例链接】

( )1. —Please be quiet. Our teacher is coming.

—It ______ be our teacher. She has gone to Beijing.

A. must B. may

C. can't D. mustn't

(2016辽宁丹东)

( )2. Yang Jiang ______ be the boy's favorite writer. He has written a lot to praise her.

A. can't B. mustn't

C. must D. need

(2016吉林长春)

( )3. —I saw your mother in the library just now.

—It ______ be her. She went to Beijing yesterday.

A. can't B. mustn't C. needn't

(2016黑龙江龙东地区)

三、情态动词一般疑问句的回答

考点一：may 表示请求时，用于主语为第一人称的一般疑问句中，其否定回答不用may not(不可以)，而用 mustn't 或can't。

考点二：在回答由must 引起的一般疑问句时，肯定回答常用must，否定回答常用needn’t 或don't have to，表示“不必”。

考点三：在回答由need 引起的一般疑问句时，肯定回答用must，否定回答用needn't。

考点四：在回答由could(请求对方许可，表示委婉语气)引起的一般疑问句时，常用can / can't回答。在回答由can引起的表示请求的一般疑问句时，用can / can't回答。

【考例链接】

( )1. —Must we finish the work today?

—______. We have something else to do tomorrow.

A. Yes, we can B. No, we can't

C. Yes, we must D. No, we needn't

(2016重庆A卷)

( )2. —Excuse me, ______ I take the magazine out of the reading room?

—Sorry, you can't. Just here, please.

A. must B. would

C. may D. need

(2016江苏淮安)

( )3. —Could you go to the bookshop with me? I want to buy The Grass House by Cao Wenxuan.

—Sorry, I ______. I've promised Mom to go home right after school.

A. can't B. couldn't

C. needn't D. mustn't

(2016江苏镇江)

（未完待续）