八年上语法课件：情态动词讲解.ppt

Grammar: Modal verbs 情态动词本身有一定的意义 无人称和数的变化 通常不带to 表示说话人的语气或情绪 语法特征 1.Ability (能力): Liu Xiang can run the 110m hurdle race within 13 seconds. can/could: 1. can 一般表示与生俱来的能力或者一种客观可能性,还可以表示请求和允许 。 Learning English _____ be difficult. can Man can not live without air. _______ I use your bike? Can can/could: 2.在疑问句中，用could可表示请求，语气较委婉。 — ____I smoke here? — Yes, you _____. No, you _____ Could can can’t/I’m afraid not can:否定推测，疑问推测 3.表示惊异、怀疑、不相信的态度。（主要用在否定句、疑问句或惊叹句中） He’s such a nice person that he ______ commit the crime. can’t 你怎么会如此地粗心！ How can you be so careless! Can this be true? can/could: 4. can never/can’t……too表示“无论怎样…也不过分”，“越…越好” 。 你过马路的时候再小心也不为过。 You can’t be too careful while crossing the road. can/be able to区别: Edison always wondered why hens could hatch (孵) chickens while he was not able to. Question: Are the two modal verbs interchangeable (互换) ? If not, why? can表示与生俱来的能力或一种客观可能，而be able to更加强调通过后天的学习和努力获得的能力，或者在某个客观的场合和背景下，能做到的事情。 Sum up 1. can 和 be able to 1) can (could) 表示能力、可能, 只用于现在时和过去时。 2) be able to可以用于各种时态。 只用be able to的情况： a.表示将能够做某事时。will be able to do sth b. 表示过去成功地做了某事时,只能用 was/ were able to do sth,不能用could。 eg: A big fire broke out in ABC hotel yesterday. Luckily, everyone __________run out of the building. was able to 2. She _____ speak both English and French. can 1. They will ______ run this machine on their own in three months. A. can B. could C. may D. be able to 2. That big cinema ______ seat 2,000 people. A. can B. should C. ought to D. is able to D A 3.(2007福建) My MP4 player isn’t in my bag. Where ___I have put it? A. can B. must C. should D. would A 4. A left-luggage office is a place where bags ____be left for a short time, especially at a railway station. A. should B. can C. must D. will B 5. Mike ___ be a policeman, for he is much too short. A. needn’t B. can’t C. should