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1、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 cant 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 ab
2、le to则有更多的时态。例如:Ill 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/cant. 此时可与may互换。在疑问句中还可用could,might(不
3、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, Im afraid not. )3、表示可能性猜测。例如:The man over there cant 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 homeworkfi
4、rst.A.wont;may B.cant must C.shouldnt;ought D.neednt; should( )2.-Do you know whose dictionary it is?-It _ Li Meis. His name is on it.A.cant B.mustt C.shouldnt D.neednt( )3.-I cant stop smoking ,doctor.-For your health,Im afraid you _.A.can B.cant C.must D.mustnt ( )4.-Is Mr.Brown driving here?-Im not sure. He _come by train.A.may B.shall C.need D.mustKEYS:BBCA2