必修三语法情态动词-公开课件.ppt

* Grammar Modal Verbs 情态动词 一、can和could的用法 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. B. 在表示能力时, 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 D 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? How can it be that …? 4.表示许可 (could可以代替can，表示语气较为婉转） Can/ Could 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. 5. 表示要求 Can you help me with this box? Can you feed the cat? 二. may和might的用法 1. 表示许可. 在表示请求允许时，might比may语气更委婉一些。用作此意时，它的否定形式可以用may not, might not，但表示“不可以”“禁止”“阻止”等意思时常用must not代替may not. 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. 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. 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 right now? 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. E. 询问对方意思时应用must Must I clean all the room? D.在间接指令中had to 取代must Mother said that the children had to be back by 4 o’clock. 四、shall 和should的用法 1. 常用于第一人称的单数和复数（I , we) 2. 表示预言。 We shan’t know the results until next week. This time next week I shall b