情态动词一can-may-must的用法.ppt

情态动词后接动词原形; 没有人称和数的变化; 不能单独作谓语, 与后面的动词共同作谓语; 其否定形式在后面直接加not。 can / can not may / may not must / must not 五.have to的用法 表示客观需要 “不得不，必须” 六need的用法 后加动词原形 表示需要，必须，用于否定和疑问句 否定：needn’t（不需要）， 疑问将need提前 What do the signs mean? Do you know? * 情态动词can, may, must的用法 Modal verbs 情态动词 Modal verbs 情态动词 can / can not 1. 表示能力(会) Mary can speak English, but she can not speak French. 2. 表示允许(可以) 也可用could (不是过去式)更委婉 Can /Could I use your dictionary? 3. 表示推测 (可能 ) ----通常用于否定形式 He can’t be in the office. I saw him go out just now. 1. S1 ___ Kitty ____? S2 _____________. 2. S1 ____ Kitty ____? S2 _____________. Can spell Yes, she can Can add No, she can’t may / may not 1. 表示允许(可以) 也可用might更委婉 May /Might I come in? 2. 表示推测 (可能) ----通常用于肯定形式 She may be still waiting for us. 3. 表示祝愿 May you have a happy weekend. may的用法: may / may not ●以may开头的疑问句，其否定回答用can’t或 mustn’t。 --May I go home now? --Yes, you may. No, you can’t/mustn’t. may not的用法: Answers: 1. May I carry your bag for you? 2. May I open the door? 3. May I get you a chair? 4. May I switch on the TV? 5. May I borrow your new bicycle? must / must not 1. must表示必须 You must do your homework first. 2. must表示 “一定”(肯定性推测 ) 语气较强 He must be at home. must的用法: must / must not 1. mustn’t表示禁止(不准；不允许) You mustn’t smoke here. 2. 以must开头的疑问句，其否定回答要用needn’t. -- Must I clean the classroom now? -- Yes, you must. No, you needn’t. must not的用法: I missed the train, so I had to take a taxi. 在疑问句和否定句中，have to需借助助动词 do ， Did he have to do it? You don‘t have to go there. （不必，不需要） ‖ needn’t 注：用于肯定句时，常作实意动词用：need to do sth Need we return the magazines today？ yes， you must./ no, you needn’t. You need not do this。 疑问句回答：同must You must not cycle. You must be careful. You must turn left. You must not enter. *