1、Unit 3 We should obey the rules Lesson 18情态动词can、may、must、need解析区别练习,情态动词,情态动词后面+动词原形,情态动词没有人称和数的变化,1,can,I can not play basketball.,I need buy a computer.,2,(能),need,(需要),She can ride a horse.,Amy need buy a book.,-,-,-,-,3,否定式构成是在情态动词后面加 not,I can play basketball.,-,can,(能),用法:,表示能力:,He can speak
2、a little English.,Can you fly?,表示请求或允许:,Can I help you?,表示猜测:,That can not be our English teacher,because she has gone to Shanghai.,could也可表示请求，语气委婉，主要用于疑问句，不可用于肯定句，答语应用can,Could I come to see you tomorrow?,Yes,you can.（否定答语可用No,Im afraid not.）,注意,用法:,表示请求或允许:,May I go home，please?,(1)以may（表许可或请求）开头
3、的一般疑问句,肯定回答用may，否定回答用mustnt或cant.(2)在疑问句中不用于第二人称,表示可能性:用在肯定句,You may be right.,No,you _,may,(可以),Yes,you may.,注意,might为may的过去式，但也可以代替may，语气较为婉转客气或更加不肯定。,You might be right.,might,mustnt/you cant.,试比较:,You may not smoke here(可能不)语气轻,You cant smoke here（不能）重,You mustnt smoke here（决不可）最重,cant,may not,m
4、ustnt,用法:,既可以做情态动词,也可以做实意动词,实意动词(need to do sth):,情态动词(need do sth):,I need buy a big house.,need,(需要),He need drive me home.,Do I need to buy a big house?,He needs to buy a big house.,Need I buy a big house?,-Yes,you must.-No,you neednt/dont have to.(不必要),-Yes,you do.-No,you dont.,用法:,表示推测“肯定，一定”:,
5、表示义务、必要或命令:,You must come early tomorrow,-Must I finish my homework first?,They must be at home.The light is on.,-Yes,you must.-No,you dont have to/neednt.,must,(必须),注意,must开头的疑问句，其否定回答通常用 dont have to 或neednt。而不用mustnt,mustnt,(禁止),否定时表示“禁止”:,You mustnt smoke here.,用法:,Its eleven oclock.I have to go
6、 now.It was getting dark.He had to finish the work first.,I dont have to go now.He doesnt have to finish the work first.,have to,(必须),注意,have to 表示客观因素We are very glad at the party,but its 11,so we have to leave now.must 表示主观因素We must study hard to find a good job for ourselves.,must,(必须),have to,mu
7、st 区别,My brother was very ill,so I call the doctor in the middle of the night.He said that they work hard.,You dont have to tell him about it.,You mustnt tell him about it.,你不一定要把此事告诉他。,你一定不要把这件事告诉他.,have to,must,had to,must,区别,Can I?Yes,you can.No,you cant.May I?Yes,you may.No,you cant/mustnt.Need
8、I?Yes,you must.No,you neednt.Do I need to?Yes,you do.No,you dont.Must I?Yes,you must.No,you neednt.,-,-,-,找伙伴,Should 应该shouldnt 不应该You should finish your homework on time.You shouldnt go to bed too late.,Exercises,1.Must we clean the house now?No,you_.neednt B.may not C.mustnt D.cant2.You return the
9、 book now.You can keep it next week if you like.A.cant B.mustnt C.neednt D.may not3.Johnny,you play with the knife,you hurt yourself.A.wont.cant B.mustnt.may C.shouldnt,must D.cant.shouldnt4._I go back before lunch?No,I dont think you_.A.Need.must B.Do.need to C.Must.have to D.May.ought to,A,C,B,C,5
10、.The teacher_ do all the exercises,but a pupil_.A.neednt.must B.may not.must C.neednt.neednt D.cant.must6.Must I finish this novel this morning?No,you_.A.mustnt B.might not C.dont have to D.cant7.The taxi _ only hold six passengers.It is full.You _ take the next one.A.may.may B.can.may C.may.can D.must.can8.This pen looks like mine,yet it isnt.Whose _ it be?A.must B.can C.may D.might,C,A,B,B,Thank you,
