情态动词课件(原创)

情态动词复习
一、can和could的用法
1. 表示能力. Tom can speak three languages.
He could walk when he was one year old.
在表示能力,能够的时候can 和be able to的区别
A. can只有现在式和过去式(could), 而be able to则有 更多的形式.
4.当是实义动词时。 A. 用法是need to do. I need to look up it in the dictionary. B. 有人称的变化。 He needs to hand in his report today. C. 否定形式：don’t need to do 疑问形式：Do you need to go on a business trip to Wuhan?---No, I don’t need to. Does she need to come ?--- Yes, she needs.
4. can用于否定句和疑问句，表示对于现在或当时 情况的否定或疑问性的猜测。 There is no light in the room. There must be nobody. He can’t be in the room. 5. Can 表示一般性的，理论上存在的可能，might而则表 示正在发生或将要发生的具体可能性。 A wise man can sometimes make a mistake. I might go to Beijing by air next week.
B. 在表示能力时, can与be able to的意义差不多,有时 两者可换用,但表示"经过努力、设法做成某事"时,要用 be able to,不可用can。
The fire spread through the hotel very quickly but everyone ____ get out. A. had to B. would C. could D. was able to 答案为D。
九、表示推测的情态动词 1. can, could, may, might, must表示在一定时间 （现在或过去）对发生和出现的事情进行推测 、猜测、判断等 . 2. must表示对现在状态的肯定判断。 The light is still on in the room. He must be working there. 3. may/might 表示对现在情况的可能性推测。 He is not here today. He may be ill.
五、will的用法
1. 可用于所有人称。 2. 表示对未来事物的预料。 You’ll be in time if you hurry. 3. 表达对目前事物的预料。 They’ll be home by this time.他们现在一定是到 家了。 4. 用于表示愿意或不愿意。 I’ll check this letter for you, if you want. We’ll not lend you any more money.
8.用于叙述目前的习惯时。 She will listen to records, alone in her room.
六、would的用法 1. would 是will的过去式, 可用于所有人称。 2. 用于提出请求时，would比will客气。 Would you pay me in cash? 3. 提出建议或邀请。 Would you like a cup of tea? 4. 用于叙述过去的习惯。 He would spend hours in the garden. 5. 句型：…would like to do sth. 想要做……
4. 否定和疑问形式。 oughtn’t to----ought not to Ought I write to say thank you? 5. Ought to 和 should 常常可以互换, 的语气稍 重一些。
八、need的用法
1. 表示必要。 If she wants anything, she need only ask. Nobody need be afraid of catching the disease. 谁都不用害怕能得这种病。 2. 当need是情态动词时没有人称的变化。 3. 否定形式：needn’t do 疑问形式: Need I go at once? No, you needn’t.
三、must和have to的用法 1. have to和must含义相似，两者往往可以互换使 用。但是有下列的不同。 A. must表示说话者命令或期待做成某事，have to用于他人发出指令或操纵的情况。 The dinner must be ready at 6:00. I must go now. You have to pass a special exam to get into the school.
2. can’t /couldn’t have done表示对过去情况的否定性推 测，表示“不可能已经做了某事”。 I can’t / couldn’t have lost the key. I never drop things.
Can/could在疑问句中表示对过去情况的疑问性推测，表 示“可能已经……了吗”？此时不能换为may或might. Someone must have broken into our bedroom. Who could have done it?

表示猜测的确定性程度 t
may might
can (could)
十、情态动词+have done 情态动词+have done, 表示推测、后悔、遗 憾、责备等语气。 1. may/might/must have done 表示对过去情况 的推测或估计，表示“可能或肯定（已经）做 了某事。 The ground is wet. It must have rained. 表示推测时，must have done 确定性最大， may have done 和might have done次之。
May I go with my friends to the harvest festival?
----Yes, you may. ----No, you mustn’t. / No, you may not./ No, you’d better not.
2. 表示可能性，有“或许”，“可能”的意思， 用might则语气更加不肯定。 He may/might be from Canada. They may/might have a lot of work to do.
4. 表示提供意见或建议。 Shall I wash the dishes now? Let’s look at it again, shall we? 5.表示命令和指示， 可用于第二、第三人称。 The students shall remain in their seats until all the papers have been collected.
5. 用于表示请求。 Will you post this letter for me, please? You’ll water the plants while I’m away. won’t you? 6. 用于发出命令或指示时。 You will carry out these instructions and report back this afternoon. 你要执行这些指示并于今日下午 报告执行情况。 7.用于叙述真理时。 Oil will float on water.
B. 两者的否定意思不同。Mustn’t表示“禁止，不允许” 。don’t have to表示“不必”. You mustn’t enter this room. You don’t have to hand it in now. C. 两者的提问方式不同。 Must I start now? Do they have to finish the homework immediately? D. must只有一种形式，have to有时态和人称的变化。 He has to come back to school at weekend. My mother had to work 12 hours a day.
D. need to be done = need doing 表示需要 被做某事。 The followers need to be watered. = The followers need watering. Exercise: Need she _____ the classroom again? A. cleans B. clean C. to clean D. cleaned
七、ought to 的用法 1. 表示责任或义务。 We ought to start at once. You ought to apologize to him. 2.表示劝告或推荐。 You ought to improve(提高) your English before going to work in America. 3.作推测性结论。 If he started at nine, he ought to be here by now.
2. 表示客观可能性 That can’t be Mary. She’s in hospital. There is someone outside. Who can it be? 3. 用于表示惊讶、疑惑或怀疑, 主要用于否定和疑问句中 Can he be serious? Where can she have put it? 4.表示许可 (could可以代替can，表示语气较为婉转） Can I read your newspaper? You can take the car, if you want. The boys could play football but the girls had to go to library.