新人教 必修3 Unit 1 Festivals around the world[情态动词课件]

Modal verbs I

情态动词的语法特征1. 情态动词有一定的意义，只表示期待或估计某事的 发生，不能表示正在发生或已经发生的事情。 2. 没有人称和数的变化，即情态动词第三人称单数不 加-s。 3. 不能独立使用，它和后面的动词构成谓语。 4. 情态动词 除ought 和have 外，后面只能接不带 to 的不定式。 5. 情态动词没有非谓语形式，即没有不定式，分词， 等形式。只作情态动词的 可情态可实义的 can/could, may/might, ought to, must need, dare/dared

可情态可助动词的 shall/should, will/would 相当于情态动词的 have to, used to

Must , can/could, may/might 的用法must

1.must 表示推测时， 只能用于肯定句。must do must be doing/do must have done 对一般时的肯定推测 对现在的动作进行肯定推测 对过去发生的事情作出的肯定判断

他们买了一辆新车。 他们一定很有钱。 They have bought a new car. They must have a lot of money.

他现在一定在看小说。 He must be reading novels now.路是湿的。昨天晚上一定下雨了。 The road is wet. It must have rained last night.

can/could1. can /could 表示推测时，只能用在否定句或疑问句中。 这么晚了，汤姆还在看书吗？ It’s so late. Can Tom be reading? 这个人不可能是玛丽， 她生病了。 It can’t be Mary. She has fallen ill.can/could have done 表对过去发生行为的可能性进行推测刚才我还看见他了， 所以他不可能出国的。 你本来可以考的更好。

“本可以，本来可能已经”用于肯定句中

I saw him just now so he couldn’t have gone abroad. You could have had a better mark.

may/might1.may/might表示推测时，只能用于陈述句，表示对现 在或将来要发生的动作把握不大。她们明天可能会到这里来。

They may come here tomorrow.

▲ might 可用于指 过去的行为 或者表示可能性更小。我问他我是否可以离开。

I asked him if I might leave. (表过去) I asked him “May I leave now?”他也许在作功课吧。

He might be doing his homework now. (可能性更小)

3.might/may have done,表示对过去发生的动作进行 可能性推测， 他可能去医务室了。 He may have gone to the clinic.

他可能已经从报纸上知道这个消息了。

He might have read about the news in the newspaper.

will/wouldWill /Would you do…? 表请求，表意志，愿望，决心If you will help me with my English, I will be very happy. I promised that I would do my best.

would表过去反复发生得动作或某种倾向“总是,总要” used to表过去常常(现在已没有这种习惯)“过去常常” used to 可与状态动词连用 would不可以 eg. He used to be a quiet boy. ( √ ) He would be a quiet boy. ( × )

shall ,should 和ought to 1.在陈述句中,shall用于二、三人称表示允诺、警告、 命令、决心等

。

You shall do as I say. (命令) Nothing shall stop me doing it. (决心) Tell him that he shall have the book tomorrow. (允诺) 2.在疑问句中,用于一、三人称，用来表示请求或征 求意见。 Shall I open the window for you?(征求意见) Shall he fetch some water for you?(请求)

3. should常表示劝告、建议、命令，与ought to意 义相近，但ought to多表示责任、义务，语气强烈。 Young people should learn how to use computers. Every citizen ought to obey law. You ought not to go. 4.should/ought to have done表示责备或批评,意 为“本应该…但”,ought to的语气更强烈,用于否定 则表示“本不该…但” You should/ought to have told her the truth earlier. She shouldn’t have left without saying a word.

5.should用于可能性推测时,表“应该，很可能” They left at 5:30. They should get there now.

1.--Excuse me, but I want to use your computer to type a report. A have my computer if you don’t --You ____ take care of it. A. shan’t B. might not C. needn’t D. 2. ---When shouldn ’tcan I come for the photos ? I need them tomorrow afternoon. B ---They _____be ready by 12 : 00 . A. can B. should C. might D. need 3. With so much work on hand, you ____to D see the game last night. A. mustn’t go B. could have gone C. shouldn’t go D. shouldn’t have gone

need1.作情态动词时,仅用于否定或疑问句,后接动词原形,表“需 You needn’t return the book now. 要”

--- Need he start from the beginning? --- Yes, he must. --- No, he needn’t/doesn’t have to.2.needn’t have done 表示做了本不必要做的事情,意为 “本不必要…”

Our color TV set is still good enough. You needn’t have bought a new one.3.need作实义动词时,表示“需要”,有人称、时态、和 数的变化 He needs to finish it this evening.

The classroom needs cleaning.