1、Unit 2 Lets celebrate！ -using language Modals(2) 情态动词表示说话人的情绪、态度或语气。 在形式上，情态动词_ 人称和数的变化。 在意义上，大多数情态动词有多个意义。 在用法上，情态动词_ 单独作谓语。 其后应接动词_ 构成谓语。 情态动词具有助动词的作用，即可用来构成否定句、疑问句及用于简略回答中。 情态动词的否定式一般在其后直接加not. 没有 不可 可以 1.表示能力 eg. I can speak fluent English now , but I couldnt last year. 2.在肯定句中，表示客观可能性，并不涉及具体某事会
2、发生，常用来说明人戒事 物的特征。要表达具体某事实际发生的可能性时，不用can，需用could，may， might。 eg. He can be very forgetful sometimes. 3.表示对现在的动作戒状态进行主观的猜测，主要用在否定句和疑问句中。 eg.Can the man over there be our head master? 4.表示惊异、怀疑、不相信等态度，主要用在否定句、疑问句和感叹句中。 eg.This cant be true. 5.表示请求和允许。表示请求，口语中常用could代替can，使语气更委婉。 特别注意： （1）could用来表示请求时，语
3、气委婉，主要用于疑问句，不能用于肯定 句，答语应用can（即：could不能用于现在时态的简略答语中）。如： Could I use your dictionary? Yes, you can.(否定回答可用：No, Im afraid not.) (2) can和和be able to辨析辨析can(could)和be able to都可以表示能力，意思上没有区别。但can 只有现在式和过去式，而be able to则有更多的形式。如：Ive always wanted to able to speak fluent English.Those bags look really heavy,
4、 are you sure youll be able to carry them on your own?但是，表示在过去某时的某一场合经过一番努力，终于做成了某 事，通常不用could，而用was/were able to来表示。这时，was/were able to相当于 managed to do或succeed in doing。如：After the accident it was a long time before she was able to walk again.The fire was very big, but most people were able to esc
5、ape from the building. (3) 惯用形式“cannot too”表示“无论怎么也不（过分）”。如：You cannot be too careful.你越小心越好。 惯用形式“cannot but+ 不定式 （不带to）”表示“不得不，只好”。如： I cannot but admire her determination.我不得不钦佩你的决心。 It was so noisy that we_hear ourselves speak. 练习 cant .I_thank you enough for what you have done for me. Youre wel
6、come. cant may&might 1.表示请求和许可，在疑问句中，might可以代替may，它表示的语气更加委婉。 -_ I have a few words with your manager? -Yes, you _. He said that I _ use his telephone. 他说我可以用他的电话。 知识拓展： may not表示“不可；不许“时，语气较强，有命令强制的意味，常可用mustnt代替，用来 回答问句“May I.?” 2. 表示推测 might和may表示对现在、将来的推测，多用于肯定句中戒否定句中。 对过去的推测要用may/might have don
7、e. might比may的可能性更小。 拓展： 1）can, could, may, might的可能性大小依次是： cancouldmaymight 2）在肯定句中，不用_ 在疑问句中，不用_ 在否定句中，cant意为_, may not意为 _. 3. may可以用于祈使句中，表示祝愿，其结构为：May+主语+动词原形“。 祝你成功！ May you succeed! Helen _ go on the trip with us, but she isnt quite sure yet. 练习 may I left my handbag on the train, but luckily
8、someone gave it to a railway official.How unbelievable it is to get it back! I mean, someone_have stolen it. might must 1.表示“必须，应该”之意，语气比should，ought to强烈。其否定形式mustnt表示“不准， 不应该，禁止”等意 eg.Everybody must obey the law. 2.在回答带有must的问句时，否定回答常用neednt戒dont have to，表示“不必”，而不 用mustnt eg.Must I come back befor
9、e ten? Yes，you must.(No, you neednt) 3.表示有把握的推测，意为“一定、准是、相必”，只用于肯定句中 eg.It must be my mother. 练习 You _ be tired after the long trip, arent you? must You_be Carol. You havent changed a bit after all these years. must 综合练习 1、If you _ smoke, please go outside. A. can B. should C. must D. may 2、- I dont
10、 really like James. Why did you invite him? - Dont worry. He _ come. He said he wasnt certain what his plans were. A. must not B. need not C. would not D. might not 3.The traffic is heavy these days. I arrive a bit late, so could you save me a place?A. can B. must C. need D. might 4.One of the few things you _ say about English people with certainty is that they talk a lot about the weather.A. need B. must C. should D. can
