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）
