新人教精通版五年级英语下册Unit 3 Lesson 17--情态动词can、may、must、need解析区别练习-课件.pptVIP

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1canI 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:① 表示能力 :He can speak a little English. Can you fly? ③ 表示请求或允许 : Can I help you? ② 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canCould I come to see you tomorrow? Yes, you can. （否定答语可用No, Im afraid not.） {{{注意{ 用法:①表示请求或允许 :May I go home，please? (1)以may（表许可或请求）开头的一般疑问句,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 ② 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. mightmustn’t / you can’t. 试比较 :● You may not smoke here．(可能不) 语气轻 ● You can’t smoke here．（不能）重 ● You mustn’t smoke here．（决不可）最重 cantmay notmustnt↓ 用法:既可以做情态动词, 也可以做实意动词② 实意动词 (need to do sth) :① 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 needn’t / don’t have to. (不必要)-- Yes, you do.-- No, you don’t. {{ 用法:② 表示推测“肯定，一定” :① 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 don‘t have to 或needn’t 。而不用mustnt mustnt(禁止)③ 否定时表示 “禁止” :You mustn’t smoke here. 用法:It’s eleven o’clock . I have to go now .It was getting dark. He had to finish the work first . I don’t have to go now . He doesn’t 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 it’s 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