情态动词专讲

• 辨析can和be able to can有现在时和过去时，be able to可用于各种 时态。can (could)表示能力时，可用be able to代替。 My mother can (is ableຫໍສະໝຸດ Baiduto) pay for the coat. 我 妈妈买得起那件外衣。 Mary will be able to tell you where she works. 玛丽会告诉你她在哪工作。 He has been able to work. 他已经能上班了。
• 注意：have/has to表示“不得不，必须”，不做 “有”讲，所以必须用助动词构成其否定形式。
1. —______ you speak Japanese? —No, I can't. • A. Can B. Must C. May D. Should 2. —Marry, _____ you play chess? —Yes, I can do it very well. I want to join the chess club. A. can B. should C. must D. need 3. —Is Mr. Brown driving here? —I'm not sure. He _____ come by train. A. may B. shall C. need D. must 4. —I can't give up smoking ,doctor. —For your health, I'm afraid you _____. A. may B. can C. have to D. must
情态动词的用法
1．常用的情态动词有can, may, must, need， 它们与动词连用一起构成谓语。 肯定句： （原形）
否定句：
（原形）
疑问句：
（原形）
（1）can的用法 1）can表示能力，“能，会” • 如：He can swim well, but I can't. • 他会游泳，而我不会。 2）表示“可能，能够” • 如：I can finish it in an hour. • 我能在一小时之内完成它。 3）表示“许可，可以”，常用在口语中。 • 如：You can use my bike. • 你可以用我的自行车。
2．will, shall的用法 （1）will在一般疑问句中表示“客气” Will you show me your picture book? 你能让我看看人的画册吗？（请求） Will you please give me a call? 请你给我打个电话好吗？ 对Will you…?的回答有以下方式： • 1）Yes, I will. (No, I won't). • 2）Sure. (I'm sorry, I can't.) • 3）All right. • 4）Certainly. (No, thank you.) • 5）Yes, please.
5. Attention, please! All the mobile phones must ______ before the meeting starts. A. turn off B. be turned off C. be turning off 6. —Let's go to the supermarket by taxi. —We _____ take a taxi. It is not far from here. A. can't B. needn't C. couldn't D. mustn't 7. Schools _______ allow students at least one hour a day for sports. A. would B. might C. should D. could 8. —Please bring your homework to school tomorrow, Steven. —OK. I _______. A. will B. won't C. would D. don't
（2）may的用法 1）表示“请求，许可”（比can正式） May I use your dictionary? 我可以用你的字典吗？ 2）表示推测，“可能，或许”（谈论可能性， 一般用于肯定句。） I may go to the market next Monday. 下周一我或许去市场。 She may be in the classroom. 她可能在教室。
（2）Shall引出的疑问句，表示客气的请求 Shall I show you my book? 我可以给你看看我的书吗？ Shall we sing the English song? 我们可以唱这首英语歌吗？ 对Shall I (we)…疑问句的回答有以下方式： • 1）Yes, please. • 2）Yes, thank you. —Shall we see a film? —No, thank you. 我们看个电影好吗？—不，谢谢。 Shall we begin with you? All right/Yes, let's. (No, let's not.) 我们从你这开始好吗？好吧。（不，不行。）
• 辨析must和have to • must侧重于个人意志和主观上的必要。 • Have to侧重于客观上的必要，用于过去 时，将来时，但must可以在间接引语中表示 过去的必要或义务。 • 如：I was ill, so mother had to send for a doctor. 我病了，妈妈只好请医生来。 • She said that she must study hard. 她说 她必须努力学习。 •
• （5）can, may, must的疑问句 • Can/May/Must+主语+v.（原形）+……？ • Can you repair the car? 你会修小汽车吗？ • Could he be a good student? 他能是名好学生吗？ • —May I borrow your ruler? 我可以借你的尺吗？ • —Sure. 可以。 对may引出的疑问句，回答可以有下列方式： 1）Yes, of course. 2）Yes, certainly. 3) Sure. 4）No, you mustn't. 5）No, you can't. 对must引出的疑问句，肯定回答用Yes, …must；否定 回答用No,…needn't.=No,…don't have to. • —Must I stay here alone? 我必须独自呆在这儿吗？ • —Yes, you must. (No, you needn't.=No, you don have to.)是的，你必须。（不，你不必。）
• •
4．have to的用法 have to表示“不得不”，“必须” （原形）
• 肯定式用 • • • 否定式用 • • • 疑问式用
（原形）
（原形）……？
如： Tom has to study Chinese, doesn't he? 汤姆得学汉语，是吧？ He doesn't have to do it right now. 他不必马上做这件事。 Did she have to work it out? 她得把这题解出来吗？ She has to stay here until her mother meets her every day, doesn't she? 她每天都要呆在这直到她妈妈来接她，是吗？
（3）must的用法 1）表示必须，“应该，应当” • You must stay here until I come back. • 你必须在这儿直到我回来。 2）表示有把握的判断或推测，“一定，准是”，一 般用在肯定句中。 • You must be a middle-school student. • 你一定是名中学生。 • It must be you.这肯定是你。 3）在“You must…”句中，此句与祈使句意思相同。 You must come here early. =Come here early! 早点 来这儿！ You must hurry up! =Hurry up! 你必须快点！
（4）can, may, must的否定形式 • can/may/ must+not+v.（原形） I can't play basketball. 我不会打篮球。 She couldn't speak until she was five years old. 她直到五岁才会说话。 May I come in? No, you mustn't/can't. 我可 以进来吗？不，你不能。 You mustn't have another baby. 你不可以生 第二个孩子。
3．would和should的区别 （1）would→will的过去式；should→shall的过去式； would you…? Will you…?表示客气的请求、劝说； would you…，更客气 Would you tell me how to get to the shop? 你能告诉我去商店怎么走吗？ Will you like to have a party? 你愿意去参加聚会吗？ （2）should+v 表示“应该” We should learn from each other. 我们应该互相学习。 You should help each other. 你们应该互相帮助。