情态动词can.doc

情态动词can
一、简介
1、结构：can + 动词原形，没有人称和数的变化。
2、否定形式：cannot/can’ t, cannot比缩略形式can’ t要正式。口语中一般用缩略形式。
例如：I can swim.
Daming can ride a bike. He can’t drive a car.
二、用法
1、表示能力（体力、知识、技能等），此时可用be able to代替。
例如：Mary can speak three languages. 玛丽会说三种语言。
= Mary is able to speak three languages.
注意：（1）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。
例如：I’ll not be able to come this afternoon. 今天下午我将会来。
（2）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。
例如：He was able to go to the party yesterday evening in spite of the heavy rain. 尽管很大雨，他昨天能来参加聚会。
2、表示请求和允许。
例如：---Can I go now?
--- Yes, you can. / No, you cannot/can’t.
此时可与may互换。在疑问句中还可用could,might（不可用于肯定句、否定句或答语）代替，不是过去式，只是语气更委婉。
例如：--- Could I come to see you tomorrow?
--- Yes, you can. ( No, I’m afraid not. )
3、表示可能性猜测。
例如：The man over there can´t be my uncle. My uncle has gone to Beijing. 那个人不可能是我的叔叔。我的叔叔去北京了。
三、练习题
( )1.---Can I go fishing with you,Dad?
---No,you _____.You ______stay at home and do your homeworkfirst.
A.won't;may B.can't must C.shouldn't;ought D.needn't; should
( )2.---Do you know whose dictionary it is?
---It ______ Li Mei's. His name is on it.
A.can't B.must't C.shouldn't D.needn't
( )3.---I can't stop smoking ,doctor.
---For your health,I'm afraid you ______.
A.can B.can't C.must D.mustn't
( )4.---Is Mr.Brown driving here?
---I'm not sure. He ______come by train.
A.may B.shall C.need D.must
KEYS：BBCA