高中語法專練：i. can, could

i. can, could

1. 基本用法

1）表示能力

Could you follow her talk?

她的報告你能聽懂嗎？

The theatre can seat 2,500 people.

這戲院可坐2500人。

2）表示許可

You can go now.

現(xiàn)在你可以走了？

Could you tell me the way to the station?

你能告訴我去火車站的路嗎？

3）表示可能性

Can the news be true?

這個消息可能是真的嗎？

We've got a map. We can't lose our way.

我們有地圖，我們不可能迷路的。

4）表示推測，can常用于否定句中

He can't be in the room, for the door is locked.

他不可能在房間里，因為門是鎖著的。

2. 在實際運(yùn)用中須注意的問題

1）表示對現(xiàn)在或?qū)砬闆r的推測時，用can't/couldn't + do或can't/couldn't be + doing,其

肯定式分別為：must do/may (might) do,或must be doing/may (might) be doing。

He can't be working , for the light is out.

他肯定不在工作，因為電燈已經(jīng)熄了。

2）表示對過去的否定猜測時，結(jié)構(gòu)為：can't/couldn't have done，肯定式分別為：must have done或may/might have done。

It couldn't have rained last night, for the ground is still dry.

昨天夜里肯定沒有下雨，因為地面仍然是干的。

3）can和be able to的用法之區(qū)別：

a. 當(dāng)表示一般能力時候can和be able to可以互換使用。

No one can do it. = No one is able to do it.

沒有人能做那件事。

b. 當(dāng)表示過去某個時候“設(shè)法或者成功做了某事”時只能用was/were able to而不能用could。

He could swim, so he was able to swim to the bank when the boat sank that day.

他會游泳，因此那天沉船時他能游到河岸。

4）“as +形容詞+ as +該形容詞+ can be”意為“到……極點”。

He is as happy as happy can be .

他高興到了極致。

5）can but do = cannot but do表示“只有，只能, 只好，不得不”。

I can but do my best. = I cannot but do my best.

我只好盡力了。

6）can't help/choose but do sth. 不得不做某事；can't help (to) do sth. 不能幫助做某事；

can't help doing sth. 情不自禁做某事。

When she calls me for help, I cannot help but do it.

當(dāng)他向我求助時，我只能出手相助。

He can't help to carry the box for me.

他不能幫我搬箱子。

He couldn't help crying at the bad news.

聽到這個消息他禁不住大哭起來。

7）cannot be/do + too = can never be/do + too無論……都不過分。

You can't be too careful while crossing the street.

you can never be too careful while crossing The street.

過馬路時你怎么小心都不過分。

She is beautiful, so you can't admire her too much .

她很漂亮，因此你怎么羨慕她都不過分。

8）can/could do with/without sth.有/沒有……就行了/可以湊合了。

She is not particular about food, so she can do with just a little bread and water.

她對食品不特別講究，因此只要有面包和水就行了。

9）could have done用于肯定句，表示對過去的一種推測“可能已經(jīng)”或責(zé)備“本來可以”；否定句中，常常表示從現(xiàn)在看過去不可能發(fā)生的事情。

I could have lent you the money. Why didn't you ask me?

我本來能借給你錢的，你為何不向我借呢？

She could have gone out with some friends.

她有可能和幾個朋友出去了。

Tom couldn't have received my letter, otherwise he would have replied before now.

湯姆不可能收到我的信件，否則他早就回信了。

專項練習(xí)

1. —Can I get you a cup of tea?

— _______.

A. That's very nice of you

B. With pleasure

C. You can, please

D. Thank you for the tea

2. —I don't think Professor Jones meant to be funny this morning, do you?

—No, although I couldn't help _______ at some of his remarks.

A. from laughing

B. to have laughed

C. but laugh

D. to laugh

3. Michael _______ be a policeman, for he's much too short.

A. needn't

B. can't

C. shouldn't

D. may

4. —Will you stay for lunch?

—Sorry. _______. My brother is coming to see me.

A. I mustn't

B. I can't

C. I needn't

D. I won't

5. —I was riding along the street and all of a sudden, a car cut in and knocked me down.

—You can never be _______ careful in the street.

A. much

B. very

C. so

D. too

答案速查　1-5　ACBBD