情态动词一can-may-must的用法

1、情态动词can, may, must的用法,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。,Modal verbs 情态动词,can / can not may / may not must / must not,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 dictio

2、nary? 3. 表示推测 (可能 ) -通常用于否定形式 He cant 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 cant,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

3、 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cant或 mustnt。 -May I go home now? -Yes, you may. No, you cant/mustnt.,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?

4、,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. mustnt表示禁止(不准；不允许) You mustnt smoke here. 2. 以must开头的疑问句，其否定回答要用neednt. - Must I clean the classroom now? - Yes, you must. No, you neednt.,must not的用法:,五.have to的

5、用法,表示客观需要 “不得不，必须”,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 dont have to go there. （不必，不需要） neednt,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：neednt（不需要）， 疑问将need提前,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./

6、 no, you neednt.,You need not do this。,疑问句回答：同must,What do the signs mean? Do you know?,You must not cycle.,You must be careful.,You must turn left.,You must not enter.,You must pay ten yuan.,You must keep silent.,You must not turn right.,You must not smoke.,.用适当的情态动词填空：。 1.I can play football. _you

7、 swim? 2.Dont worry. You _ return me this book tomorrow. 3.My grandma is ill. You _ talk so loudly here . 4.I cant play with you. I _finish my homework first. 5.I_ get up early tomorrow. because I have a meeting. 6._you please open the window?,Can,may,cant,must,must,Can,9. Nobody _live without air.

8、10._he speak Chinese ?Yes ,a little. 11. The book _ be returned before Saturday. 12._I come in ?Yes ,please. 13. You _give up smoking at once. Its bad for your health. 14. Excuse me ._I ask you a question? 15. _you tell me where the station is ? 16. _ I finish the work now ?No, you _. You _ do it this evening. 17. May I use your dictionary ? Sorry , you _. I am using it