1、1、be 动词的用法既可作系动词,又可作助动词,做助动词有人称和数的变化,第一人称用am,第二人称及复数用are,第三人称及单数用is, am,is 过去式为was, are的过去式为were,它与现在分词构成进行时态和过去分词一起构成被动语态。a. 表示时态 be+doing(现在分词)表示现在进行的动作He is singing. 他正在唱歌。b. 表示语态 be+done(过去分词) 表被动语态He was sent to England. 他被派往英国。c. be+to do(动词不定式)表示计划安排命令。 We are to plant trees next week. 下周我们将要
2、去植树。 You are to explain this 。对此你要做出解释。二、do的用法Do主要帮助实意动词构成否定和疑问句,后跟动词原形,有时放在实意动词前起强调作用,还可代替前文出现的动词,避免重复。Do有人称和数的变化,第一、二人称及复数用do,第三人称及单数用does,过去式为did。1)构成一般疑问句。 DO +主语+动词原形 +其他 I like singing 变为疑问句为 Do you like singing ?2)do + not 构成否定句。主语+do +not +动词原形。 I do not want to be criticized. 我不想挨批评。 He doe
3、snt like to study. 他不想学习。 Many students didnt know the importance of English before. 过去好多学生不知道英语的重要性.3) 构成否定祈使句。 Dont go there. 不要去那里。 Dont be so absent-minded. 不要这么心不在焉。说明:构成否定祈使句只用do,不用did和does。4)放在动词原形前,加强该动词的语气。 Do come to my birthday party please.请一定来参加我的生日宴会。 I did go there. 我确实去那儿了。 I do miss
4、 you. 我确实想你。我真想你了!5)用作代替动词。 - Do you like Beijing? -你喜欢北京吗? - Yes, I do. No,I dont. -是的,喜欢。(do用作代动词,代替like Beijing.) He knows how to drive a car, doesnt he? 他知道如何开车,对吧?3、have 的用法Have+过去分词 构成完成时态I have studied english for a long time .情态动词的基本用法归纳情态动词有can (could), may (might), must, have to, shall (sh
5、ould, will (would), dare (dared), need (needed), ought to等。 情态动词无人称和数的变化;不能单独使用,必须与其后的动词原形构成谓语。一、 can, could1) 表示能力Mary can speak three languages. Can you skate?此时可用be able to代替。Can只有一般现在时和一般过去式;而be able to则有更多的时态。Ill not be able to come this afternoon.当表示“经过努力才得以做成功某事”时应用be able to,不能用Can。如:He was
6、able to go to the party yesterday evening in spite of the heavy rain.2) 表示请求和允许。-Can I go now?- Yes, you can. / No, you cant.此时可与may互换。在疑问句中还可用could,might代替,不是过去式,只是语气更委婉,不能用于肯定句和答语中。- Could I come to see you tomorrow?- Yes, you can. ( No, Im afraid not. )3) 表示推测(惊讶、怀疑、不相信的态度),用于疑问句、否定句和感叹句中。Can thi
7、s be true?This cant be done by him.How can this be true?二、 may, might1) 表示请求和允许。might比 may语气更委婉,而不是过去式。否定回答时可用cant或mustnt,表示“不可以,禁止”。-Might/ May I smoke in this room?- No, you mustnt.- May/Might I take this book out of the room?- Yes, you can. (No, you cant / mustnt. )用May I.?征徇对方许可时比较正式和客气,而用Can I.
8、?在口语中更常见。2)用于祈使句,表示祝愿。May you succeed!3) 表示推测、可能性(不用于疑问句)。might不是过去式,它所表示的可能性比may小。1He may /might be very busy now.2Your mother may /might not know the truth.三、 must, have to1) 表示必须、必要。You must come in time.在回答引出的问句时,如果是否定的,不能用mustnt(禁止,不准),而用neednt, dont have to(不必).- Must we hand in our exercise b
9、ooks today?- Yes, you must.- No, you dont have to / you neednt.2) must是说话人的主观看法, 而have to则强调客观需要。Must只有一般现在时, have to 有更多的时态形式。1 he play isnt interesting, I really must go now.2 I had to work when I was your age.3) 表示推测、可能性(只用于肯定的陈述句)1 Youre Toms good friend, so you must know what he likes best.2 Yo
10、ur mother must be waiting for you now.四、 shall, should1) shall +动词原形 表示将来时态Shall we go shopping tomorrow?2) shall 用于第一人称,征求对方的意见。What shall we do this evening?shall 用于第二、三人称,表示说话人给对方的命令、警告、允诺或威胁。1. You shall fail if you dont work hard.(警告)2. He shall have the book when I finish it.(允诺)3. He shall be
11、 punished.(威胁)六、 will, would1) 表示请求、建议等,would更委婉。 Would you like a cup of coffee? 你想要一杯咖啡吗?2) will +动词原形 表将来时态 He will come back next month . 他下个月将会回来。3)表示意志、愿望和决心。1. I will never do that again. 助动词练习题1 把下列句子变为一般疑问句。1. It is a lovely dog. _2. She is lovely girl.3. We are classmates. _4. I am a docto
12、r. 5. There is a bird in the tree. _6. They are good friends. _7. I love my parents. _9. We have a pleasant home. _ 10.They go to church on Sunday. _ 11.You are a singer. _ 2. 用do does be 填空 1 _ she know all the answers ? Yes , she _ . No, she _.2 _ the twins often fight ? Yes ,_ do. No, _ dont.3 _ your dad like listening to music? Yes ,_ does . No, _ doesnt. 5 _ you have a new teacher? Yes , I _. No, I _. 6 _ she a teacher? Yes, she _ . No, she _.10 _ your father
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