背出情态动词要点

1、情态动词 Modal verbs情态动词表示说话人对某一动作或状态的态度，认为可能、应当、必要等等，情态动 词没有人称和数的变化。1can 和 could (could 是 can 的过去式。 )(1) . 表示“能力 ”、“许可”、“可能性 ”(用于疑问句或否定句中) 。Can she drive a bus?Can it be trueThe teacher can't be in the office.?(2). could 可以用来比较委婉地提出问题。Could you help me with my English ?(3) can 和 be able to 意思上没有区别

2、.was / were able to do=succeeded in doing sth. 表示过去成功做成某事 .A fire happened to the hotel last night but luckily everyone was able to get out.2 may 和 might (might 是 may 的过去式。 )(1) 表示允许或征询对方许可，有 可以"的意思。否定式 may not,也可用must not = mustn '但常用 mustn't 来表示 “不可以 ”、“禁止 ”、“不允许 ”等意思。May I watch TV a

3、fter supper?Yes, you may.No, you may not (mustn't) .在请求对方许可时，Might I更礼貌 一些。Might I have your name ?(2) 表示可能性, “或许 ”、“可能 ”(用在肯定句中 )。 Might 表示语气更加不肯定。He may / might come today 3.must 和 have to(1) 表示“必须”、“应该 ”。否定式 must not (mustn '表示 不许可” 不准” 禁止"等。Everybody must obey the rulesYou mustn'

4、;t lend it to others回答“must'的问句时，否定式 needn't，表示 不必”不用 must not,Must I be home before eight o'clock? Yes, you mustNo, you needn't (You don ' t have to.) ( 2)表示“偏偏,总是'Why must you always leave your dirty clothes in the bedroom?Why must it rain on New Year 'Day?(3) have to 表

5、示 “必须'、 “不得不 ',have to表示客观需要。have to有更多的时态形式。must表示的是说话人的主观看法。You must work hard at your lessons主观看法 )I have to go now. (客观需要 )(4) 表示推测“一定' “必定'(用在肯定句中)The teacher must be in his office.He must be doing his homework now.4need 和 dare(1)need表示 需要” 必需”。常用在否定句或疑问句中。Need she go there at o

6、nce ? Yes, she must. No, she needn't.(2) dare/dared 表示“敢”通常用于否定句、疑问句和条件从句中。Dare she go home alone at night? Yes, she dare. No, she daren't.注：need和dare也可用作行为动词。后接动词不定式。Does he need to clean the room now ? Does she dare (to) go home alone?How dared they say such a thing ?5.shall 和 should(1) sh

7、all 用于第二, 三人称, 表示说话人的意愿，有 “命令”、“警告”、“威胁”、“强制”、“允诺”等意思。You shall do as 1 say.(强制)You shall not touch my things警告)All the students shall wait outside. You shall get a new bike if you do well in the exam.(2) 在疑问句中，shall用来征询对方意见或请求指示，用于第一、三人称。Where shall I wait for you?Shall he come at once?(3 ) should

8、作为情态动词，表示 “应该”。He should be here at any moment. You should keep your word(4) 表示惊奇作“竟然”解It is strange that he should come to school late.6will 和 wouldAwill(1) will 表示“意志”、 “意愿”，可用于各种人称。If you will help me, I shall be grateful to you.(2) will 在疑问句中用于第二人称时，表示询问对方的意愿或向对方提出请求。Will you please give him a m

9、essage when you see him?(3) 表示习惯性动作，有 “总是”、 “惯于”的意思。Fish will die out of water.I push the door, but it won'topen.The girl will often spend the evening with her mother Bwould(1) would 是 will 的过去式，表示过去时间的 “意志”、 “愿望”,用于各种人称。They said that they would help us(2) 表示说话人的意愿或向对方提出请求 .Would you like/love

10、to see a film?Yes, I'd like/love to.No, I don'tthink I would.(3) 表示过去的习惯性动作。She would sit like that for hours.7. Ought to 表示义务，“应该”、“应当”等否定式为 ought not to (oughtn'tto)，疑问式为 Ought I to? Ought he to go? Yes，he ought to8. used to do.过去常常 ”疑问式是 Used he to ?否定式是 used not to 或 use(d)n 't t

11、o 也可用 didn't use to.He used to get up very early in the morning.He used to get up very early in the morning, usen't he ?/ didn 't he ?There used to be a bus stop on that corner, usedn'tthere /didn'tthere ?A. 对现在情况的推测.1. must用在肯定句中，表示对当前发生的事或情况做出很肯定”的推测，可译作 准是”、一定是”、等。疑问和否定分别用 can

12、和can' t . can'常译作 不可能”You must be very tired after the long walk.He has made great progress. He must be working very hard.There is no light in the room.She can'tbe at home.2. mightmaycould 用于肯定句，表示对当前发生的事或情况做出 “不太肯定”的推测， “也许”、 “有可能”。He might/ may/ could be in the lab.也许他在实验室里。She hasn

13、9;t come back；she mightmaycould be very busy today注意：* may not / might not 表示 可能不”He may not know the news now. They might not stay at home.B. 对过去情况的推测1. must have done 指过去 一定已做过 ”It must have rained last night , didn 'tit ?They must have lived here for 10 years, haven'tthey ?2. can ' t

14、/ couldn ' t have指过去不可能做过 ”The workers can 't have finished their work yesterday.3. * can / could have done在疑问句中表示对过去发生的事情的怀疑或不肯定. 可能”Can the workers have finished their work yesterday?4. may /might have done 用在肯定句中，表示过去"可能.” Tom hasn't arrived yet. He may / might have missed the tr

15、ain.5. *might/could have done 在肯定句中表示"过去本来能做 ，而实际上却没有做.”You might have been more careful.He could have passed the exam， but he didn't study hard.这里的may与might, can '与couldn'在时间上无甚差别，只是后者在语气上比前者婉转， 但需注意下面句中的用法。He said that she might have missed the train.（主句中，动词 said是过去时，从句中只能用might。）He thought that she couldn 't have missed it .（主句中，动词thought是过去时，从句中只能用 couldn't。）6.ought to / should have done 表"过去应该做某事而实际上没有做到，含有责备的意思.You should