5.must的用法 情态 动词 | 用法 | 例句 | must | 表示说话人的主观看法，“必须、必要”。
在回答引出的问句时，如果是否定的，不能用mustn’t（禁止，不准），而用needn’t, don’t have to（不必）.
| You must come in time.
---- Must we hand in our exercise books today?
---- Yes, you must.
---- No, you don’t have to / you needn’t.
| 3) 表示推测、可能性（只用于肯定的陈述句）
| 1． You’re Tom’s good friend, so you must know what he likes best.
2． Your mother must be waiting for you now.
| “偏偏，非得，硬要”做某事 | If you must smoke, please go out. | | Mustn’t表禁止 | You mustn’t smoke here. |
二．归类讲解 1.must, may (might) 和can表示“推测”的用法 情态 动词 | 用法 | 例句 | must | 只能用于肯定句，表示可能性很大的一种推测，作“肯定”“一定”讲 | (1)— Look, someone is coming. Who can it be? — It may be the headmaster. —It can’t be him. He has gone to Shanghai. — Then it must be Mr. Zhang. He looks like the headmaster. (2) — Can they have finished the work? — No, they can’t have finished the work so soon. | May /might | 用于肯定句中（可能，或许，大概）；用于否定句中（可能不）。表示可能性较小的一种推测 | can | 表示推测时，只用于否定句和疑问句中 |
2 情态动词的用法：表示“应该”、“必须”命令和建议
Must 用于表示“必须”、“务必”：
You must keep the place clean. 你务必保持地方干净。
Shall 和 Should 用于表示“必须”： Each member shall wear a name card. (表示规定) 每一个会员必须配带名卡。
The rules shall take effect on Jan. 1st. (shall 用于规章等，表示义务和规定)新规则于一月一日起生效。 3. 情态动词+完成式 could/can have done 本来可以；有可能
needn’t have done 本没必要做某事
should / ought to have done 本应该做某事
shouldn’t / oughtn’t to have done本不应该做某事 must have done 肯定做了某事（无否定形式） 4. 表请求和允许
Can/Could I ask you something ? 我可以问你一件事吗？ May/Might I make a suggestion ? 我可以提个建议吗？
Will you kindly tell me the way to the post office ? 请问到邮局怎么走？(表示客气请求)
Would you give me your address ? 请你告诉我你的地址，好吗？
Shall we talk? 我们谈谈好吗？ 三尝试演练，合作解疑。 1. —It must be Mr. Li who did it. —No, it _____ be Mr. Li. A. mustn’t B. can’t C. wouldn’t D. may 2. —It’s getting cloudier and cloudier. —Yes, I’m afraid it ______ be raining soon. A. must B. should C. might D. can 3. I promised to get there before 5 o’clock, but now the rain is pouring down. They _____ for me impatiently. A. may wait B. ought to wait C. could wait D. must be waiting 4. —______ you make so much noise? —Sorry, I’ll take care not to. A. Must; B. Can C. May D. Would 5. On Sundays when I was a child, Father and I _____ get up early and go fishing. A. could B. would C. might D. should 四当堂检测，拓展延伸。 1．—Shall I tell John about it? —No, you ______. I’ve told him already. A. needn’t B. wouldn’t C. mustn’t D. shouldn’t 2. —Why didn’t you come to see me? —I ______, but I was too busy yesterday. A. like to B. should like to C. would like to have D. am going to 3. You can’t imagine that a well-behaved gentleman __ be so rude to a lady. A. might B. need C. should D. would 4. There was plenty of time; she ______. A. mustn’t have hurried B. needn’t have hurried C. may not have hurried D. wouldn’t have hurried 5. When the old man was alive, he ______ sit for hours at the door. A. would B. could C. must D. might 五．堂小结，布置作业。 背过情态动词用法，完成课后练习题。 课后巩固案 1. — When can I come for the photos? I need them tomorrow afternoon. — They_________ be ready by 12:00. A. can B. should C. might D. need 2. — You know that you were driving 100 km an hour, don’t you? — No officer, I ____. This car doesn’t do more than 80. A. may not have been B. couldn’t have been C. mustn’t have been D. shouldn’t have been 3. I think he could have joined us, but he ____ A. doesn’t B. did C. didn’t D. couldn’t 4. — You must phone us every week. — Yes, I _____. A. must B. have to C. will D. should 5. He was taken away by the police. He ___ for a robber. A. must be mistaken B. was being mistaken C. must mistake D. must have been mistaken 6. You buy a gift, but you can if you want to. A. must B. mustn’t C. have to D. don’t have to 7. I have told you the truth. ______ I keep repeating it? A. Must B. Can C. May D. Will | 
