情态动词讲 解 最好版精典课件.ppt

Modal Verbs;can/could 1. 表示“能力”， 此时could是can的过去式 与be able to 的区别 can/could 只表示有能力做某事 be able to 表示有能力做并且确实做到了 2. 表示惊异、怀疑、猜测 （多用于否定句和疑问句中） could/can 此时表示语气强弱或可能性大小。 How can you be so rude? Michael can’t be a policeman, for he is much too short. 3. 表示“请求、许可” 翻译成“可以” 此时could语气更委婉。 Can/could I use your car tomorrow? You can borrow some books from the library. 4. 有时会，偶尔会 It can be quite cold in May. ;may/might 1. 表示“请求、许可”， might 语气更委婉，此时可与could/can 互换 May I ask you for help? 2. may 放到句首时表祝愿 May you succeed!/ May God bless you! 3. 表推测 “也许、可能” He may come here tomorrow. may well do 很可能 may/might as well do 最好，不妨;must 1. “必须” 否定式：mustn’t 不应该、不许可、不准、禁止 You must hand in your homework before the class is over. needn’t /don’t have to “不必” 2. 肯定式表示对现在或过去的推测，“一定” must be doing sth./must have done sth. He must be waiting for us now. He must have seen the film. 3. “非得、偏要” （常用于疑问句/条件状语从句中） Must I play the piano at home, mum? If you must know, her name is Lucy.;must 与have to do 的区别: must 表示说话人的主观看法 “必须” have to do 表示客观上需要，不得不做某事，有人称、数和时态的变化。;should/ought to 1. 表示责任或义务上“应该” ought to 的语气更强 should 含有建议、劝告的意味。 2. should 表推测 “应该” 3. 竟然 I can’t imagine that he should behave so rudely at the party. 4.万一(if条件从句中) If the computer should break down, we’ll at the expenses. ;will/would 1. 表示“请求、建议” would 语气更委婉 Will/would you please open the door? Would you pass me the book? 2. 表示意愿、意志和决心。 此时would 是will的过去式 I will never do that again. He said he would help us out of trouble. 3. would 表示过去经常发生或习惯性的动作，“总是” He would go swimming in summer when he lived in the countryside. used to do过去常常…但现在已不再…;情态动词+have done 表示推测和虚拟 1. must have done 只用于肯定句中，表示对??去情况肯定的推测 2. should have done _________________________________ _________________________________ 3. shouldn’t have done __________________________________ __________________________________ 4. can/could have done ___________________________________ ____________________________________;5. can’t/couldn’t have done _____________________________