摘要：1．对现在或将来的推测用“情态动词+动词原形 . 肯定的推测一般用must.should.may .其中.must的语气最强.意为“肯定 .“准是 .“想必是 ,should的语气次之.意为“很可能 .“应该 .指按常理推测,may的语气最弱.意为“有时会 .“也许 .“可能 . 否定推测分为两种情况:语气不很肯定时.常用may／might／could not.意为“可能不 .“也许不 ,否定语气较强时.则用can't.意为“根本不可能 .“一定不能 .表示惊异.怀疑的感情色彩. [考例]You be tired after working for eight hours without a rest. [广东省] A. can B. may C. must D. need [答案]C.[解析] 本题考查情态动词must.can.may.need的区别.本题由题意人手.“你工作了八个小时没有休息肯定很累. 情态动词must在此表示肯定的推测. 一Look at the boy running on the ground．Is it Davis? --It be him．I saw him go to the teacher's office just now．[黄冈市] A． must B can't C．could D．might [答案]B.[解析] 考查情态动词.表推测时否定句中用can't.表示“不可能 .因为他已经去了老师的办公室. [语法回顾] 1 情态动词的语法特征 1) 情态动词不能表示正在发生或已经发生的事情.只表示期待或估计某事的发生. 2) 情态动词除ought 和have 外.后面只能接不带to 的不定式. 3) 情态动词没有人称.数的变化.即情态动词第三人称单数不加-s. 4)情态动词没有非谓语形式.即没有不定式.分词.等形式. 常见的情态动词有:can , must ,shall , dare , need等,另外,have to.had better也当作情态动词使用.情态动词后面必须加动词的原形. can 和be able to 1)can/could 表示能力,可能 , 只用于现在式和过去式.be able to可以用于各种时态.例如: They will be able to tell you the news soon. 他很快就能告诉你消息了. 2)只用be able to的情况: a. 位于助动词后. b. 情态动词后. c. 表示过去某时刻动作时. d. 用于句首表示条件. e. 表示成功地做了某事时.用was/were able to.不能用could.例如: He was able to flee Europe before the war broke out. = He managed to flee Europe before the war broke out. 他在战争爆发之前逃离欧洲. 注意:could有时不表示时态 1)提出委婉的请求.(注意在回答中不可用could).例如: --- Could I have the television on? 我能看电视吗? --- Yes, you can. / No, you can't. 可以/不可以. 2)在否定句.疑问句中表示推测或怀疑.例如: He couldn't be a bad man. 他不大可能是坏人. may和might www.zk5u.co 1) 表示允许或请求,表示没有把握的推测,may 放在句首.表示祝愿.例如: May God bless you! 愿上帝保佑你! He might be at home. 他可能在家. 注意:might 表示推测时.不表示时态.只是可能性比may 小. 2) 成语:may/might as well.后面接不带to 的不定式.意为"不妨".例如: If that is the case, we may as well try.如果情况确实如此.我们不妨试一试. have to和must 1) 两词都是'必须'的意思.have to 表示客观的需要.must 表示说话人主观上的看法.既主观上的必要.例如: My brother was very ill, so I had to call the doctor in the middle of the night. 弟弟病得很厉害.我只得半夜里把医生请来. He said that they must work hard. 他说他们必须努力工作. 2) have to有人称.数.时态的变化.而must只有一种形式.但must 可用于间接引语中表示过去的必要或义务.例如: He had to look after his sister yesterday. 他昨晚只得照顾他姐姐. 3) 否定结构中:don't have to表示"不必".mustn't表示"禁止".例如: You don't have to tell him about it. 你不一定要把此事告诉他. You mustn't tell him about it. 你不得把这件事告诉他. must表示推测 1) must用在肯定句中表示较有把握的推测.意为"一定". 2) must表对现在的状态或现在正发生的事情的推测时.must 后面通常接系动词be 的原形或行为动词的进行式.例如: You have worked hard all day. You must be tired. 你辛苦干一整天.一定累了. He must be working in his office. 他一定在办公室工作呢. 比较:He must be staying there. 他现在肯定在那里. He must stay there. 他必须呆在那. 3) must 表示对已发生的事情的推测时.must 要接完成式.例如: I didn't hear the phone. I must have been asleep. 我刚才没有听到电话.我想必是睡着了. 4) must表示对过去某时正发生的事情的推测.must 后面要接不定式的完成进行式.例如: ---Why didn't you answer my phone call? 为何不接我的电话? ---Well, I must have been sleeping, so I didn't hear it.唉.肯定在睡觉.所以没有听见. 5) 否定推测用can't.例如: If Tom didn't leave here until five o'clock, he can't be home yet. 如果汤姆五点才离开这儿.他此时一定还未到家. 表示推测的用法 can, could, may, might, must 皆可表示推测.其用法如下: 1)情态动词+动词原形.表示对现在或将来的情况的推测.此时动词通常为系动词.例如: I don't know where she is, she may be in Wuhan. 我不知道她在哪儿.可能在武汉. 2)情态动词+动词现在进行时.表示对现在或将来正在进行的情况进行推测.例如: At this moment, our teacher must be correcting our exam papers. 这时.想必我们老师正在批改试卷. should 和ought to 除了上述的用法.两者还可表示"想必一定.按理应该"的意思.例如: I ought to be able to live on my salary. 靠我的薪水.想必也能维持了. It ought to be ready now. 想必现在准备好了吧. They should be there by now, I think. 现在他们该到那儿了. The poems should be out in a month at most. 诗集估计最多还有一个月就要出版了. had better表示"最好".相当于一个助动词.它只有一种形式.它后面要跟动词原形.例如: It is pretty cold. You'd better put on my coat. 天相当冷.你最好穿上我的外套. She'd better not play with the dog. 她最好不要玩耍那条狗. would rather表示"宁愿"www.zk5u.co would rather do would rather not do would rather- than- 宁愿-而不愿. 还有would sooner, had rather, had sooner都表示"宁愿"."宁可"的意思.例如: If I have a choice, I had sooner not continue my studies at this school. 如果有选择的余地.我宁可辍学离开这个学校. I would rather stay here than go home. = I would stay here rather than go home. 我宁愿呆在这儿.而不愿回家. will和would 注意:1)would like,would like to do = want to 想要.为固定搭配.例如: Would you like to go with me? 想和我一块去吗? 2)Will you-? Would you like-? 表示肯定含义的请求劝说时.疑问句中一般用some, 而不是any.例如: Would you like some cake? 吃点蛋糕吧. 3)否定结构中用will.一般不用would, won't you是一种委婉语气. Won't you sit down? 你不坐下吗? 情态动词的回答方式 问句 肯定回答 否定回答 Need you-? Yes, I must. No, I needn't Must you-? No, I don't have to. 带to 的情态动词 带to 的情态动词有四个:ought to, have to, used to, be to, 如加上have got to , be able to.为六个.它们的疑问.否定形式应予以注意: Do they have to pay their bill before the end of the month? 他们必须在月底前付帐单吗? She didn't use to play tennis before she was fourteen.在她十四岁前.她不会打网球. You ought not to have told her all about it.你不应该告诉他所有这件事. Ought he to see a heart specialist at once.? ought to 本身作为情态动词使用.其他的词作为实义动词使用.变疑问.否定时.须有do 等助动词协助. need和dare www.zk5u.co 这两词既可做实义动词用.又可做情态动词用.作为情态动词.两者都只能用于疑问句.否定句和条件句.need 作实义动词时后面的不定式必须带to.而dare作实义动词用时, 后面的to 时常可以被省略. 1) 实义动词:need need + n. / to do sth 2) 情态动词:need.只用原形need后加do.否定形式为need not.例如: Need you go yet? 你要走了吗? Yes, I must. / No, I needn't.是的.我要走了/不.不急着走. [语法过关]

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