可以
(一) can和could的用法
1.表示能力。例如:
Can you finish this work tonight ?
Man cannot live without air .
2.表示请求和允许。例如:
Can I go now ?
You can have the book when I have finished it .
3.表示可能性(可以,可能)。例如:
We can call for you at nine .
You can’t sell the cow and drink the milk, as the saying goes .
4.表示推测某人或某物一时的情况(有时候会……)。例如:
SARS can be very dangerous .非典型肺炎会很危险。
He can be very friendly at times .他有时会很友好。
The road can be blocked .路可能会被堵塞了。
Our house is on the top of the hill, and in winter the winds can be pretty cold .
5.表示惊异、怀疑、不相信的态度(主要用在否定句、疑问句或感叹句中)。例如:
Can this be true ?
How can you be so careless !
This cannot be done by him .
注意:can的将来时,可用be able to代替。例如:
I’ll not be able to come this afternoon .
但当我们要表示“某件事已做成功”时,应用was(were) able to,不能用could。例如:
He was able to go to the party yesterday evening and he enjoyed himself very much .
6.could表示客气地提出要求或陈述看法。例如:
Could you come and see next Sunday .
I’m sorry I couldn’t lend you the book now .
7.could也可以表示请求,语气较委婉,主要用于疑问句,不用于肯定句,答语应用can。
例如:
—Could I come to see you tomorrow ?
—Yes, you can .(否定句答语可用:No, I’m afraid not .)
8.注意can的惯用语。
1) cannot but +原形动词,意为:“不得不”。例如:
I cannot but tell her the truth .
2) Cannot help +动名词,意为:“不得不”。例如:
I cannot help laughing .
3) Can but +原形动词,意为:“只好;不得不”。例如:
We can but agree with him .
4) Cannot … too意为:“怎么……也不为过;不嫌太过……”。(参阅形容词和副词)
A man cannot have too many ties .男人有再多的领带也不为过。
(二)may和might的用法
1.表示许可。表示请求、允许时,might比may的语气委婉。否定回答时可用can’t或mustn’t,表示“不可以”、“禁止”、“阻止”之意。例如:
—Might I use your pen ?
—No, you mustn’t .
—May I take this book out ?
—Yes, you can .(No, you can’t (mustn’t) .)
用May I …征询对方许可,在文体上比较正式,在语气上比较客气。在日常口语中,特别在现代口语中,用Can I …征询对方意见更为常见。
2.用语祈使句,表示祝愿。例如:
May you succeed !
3.表示推测,意为“可能”(不用于疑问句)。从语气上判断,may所表示的可能性比might大一点,而might则表示较多的怀疑。例如:
He may be very busy now .(可能性较大)
He might be very busy now .(可能性较小)
It may rain this afternoon .(可能性较大)
It might rain this afternoon .(可能性较小)
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