情态动词can在英语中的使用频率较高,主要用法和考点有:
一、表能力(ability)
此时,can表示“会,能够”。否定句直接在can后面加not,疑问句则将can提到句首。如:
肯定句:She can drive a car. (她会开车。)
否定句:She cannot/can"t drive a car.
一般疑问句及其回答:Can she drive a car? Yes, she can. / No, she can"t.
划线部分提问:What can she drive? (假如划线部分为a car的话)
【注意】can与be able to
1、be able to只能表示“会,能够”,但can还有其他意思,请参考接下去can的其他几种用法。
2、can只有现在时和过去时两种形式,而be able to则有多种时态形式。如:
Will you be able to come tomorrow? (你明天能来吗?)
This factory has been able to produce newly-devised sewing machines. (这家工厂已能生产新设计的缝纫机了。)
3、在be able to之前可加用另外一个助动词,且多用于否定或疑问结构,而can则无此用法。如:
He may be able to come tomorrow morning. (他明早可能能来。)
4、用于否定结构, be able to表达一时情况,而can则表达往常情况。如:
He is not able to swim today. (他今天不能游泳。)
He can"t swim at all. (他根本不会游泳。)
5、be able to后可接系表结构,表示一种状态或性质,而can没有这种用法。如:
He was able to be cold about her now. (他现在对她可能有些冷淡。)
6、be able to有非谓语动词形式(即接在动词不定式或是以动名词或分词的形式出现),而can则没有。如:
I hope to be able to do the work. (我希望能做这项工作。)
Being able to sing well, he decided to take part in the singing contest. (因为擅长唱歌,他决定参加歌唱比赛。)
He left the classroom sadly, without being able to answer six of the questions of the test. (他难过地离开了教室,有六道题没答出。)
二、表许可(permission)
此时,can表示“可以”。如:
Can you lend me a pen? (能借我一支笔吗?)
He can leave now. (他现在可以离开了。)
【注意】can与may
注意对比:
Can I help you?
May I help you?
may的语气更加委婉。
三、表猜测(guess)
can如果要表猜测一定要用否定形式can"t,表示可能性比较大的猜测。如:
对过去时间:He can"t have gone to Paris. I saw him on the street just now. (他不可能已经去巴黎了。我刚才在街上看到他了。)
对现在时间:He can"t be reading in the library now. (他现在不可能在图书馆看书。)
【注意】can"t与must
can"t表示否定猜测,must表示肯定猜测。如:
对过去时间:He must have been to New York many times, because he knows it very well. (他一定去过纽约很多次了,因为他对纽约了如指掌。)
对现在时间:He must be cleaning the classroom now. (他现在肯定在打扫教室。)
四、趣味用法
can有时也会用作实义动词,表示“装罐”;此时,can也可以作为名词,表示“罐头”。如:
He can can the can he can can.
这句话乍一看,让人晕头转向,但真要看懂,关键在于要明白can可以用作实义动词和名词。
句中的第1个和第4个can是情态动词,表示“可以,能够”。第2个和和第5个can是实义动词,表示“装罐”。第3个can是名词,表示“罐头”。而句中the can后面的he can can实际上是the can的定语从句,省略了that或which。
所以,原句的意思是:
他能装他会装的罐头。