can和could的意义,有能力做,有可能,可以
She can lift me up with one hand . 她可以一只手把我举起来。(有能力做)
Can yon swim ? 你会游泳吗?(有能力做)
You can borrow my car if you want to.如果你想借我的汽车,你可以借去用。(有可能)
Anybody can learn to cook. 人人都能学会做饭。(可以)
It could rain later. 晚些时候可能会下雨的。(有可能)
Could 不仅是can 的过去时形式,could 还可以用来表达现在和将来。
You could be right. 你可能是对的。
Could I see you tomorrow evening ? 明天晚上我可以见见你吗?
关于can 、be able to 和could 表示“能力”的用法需要注意下面几点:
1、现在和将来
can 通常用来表达现在或“一般的能力”——即你无论什么时候想做就能做到的能力。
Look! I can do it ! I can do it !嗨,我会做这事啦!我会做啦!
You can certainly cook , even if you can’t do anything else. 你当然会做饭,即使你别的事一样也不会。
be able to 也可以用,但不如can 用得经常。
You are certainly able to cook .
当要表达将来的能力时,一般要用will be able to ……
I’ll be able to speak German in another few months. 再过几个月我就会说德语了。(不能说:“I can speak ……”)
One day people will be able to run a kilometer in two minutes .总有一天人们会两分钟跑完一千米的。
If I have a good sleep I’ll be able to work out the problem.如果我睡个好觉,我就可以作出这个习题。
但是,当人们现在决定将来是否有做某事的能力时,can 常常也是可以用的。
We’re too busy today ,but we can repair your car tomorrow .我们今天太忙了,但是明天我们可以给你修汽车。
We can talk about that later . 这一点咱们以后再谈。
Can you come to a party on Saturday ?星期六有个聚会,你能来吗?
2、过去
could 用来表达“一般的能力”——即你过去想干什么就可以干什么。(was /were able to 也可以用来表达这个意思。)
She could sing like an angel when she was a kid .当她还是个小孩子的时候,她可以唱得象天使一般好听。(也可以说she was able to sing ……)
My father could speak ten languages. 我父亲从前会说十种语言。
不能用could 表达过去某种具体的能力(即在某一个场合做某事的能力),此时需要用 was able to , managed to , 或 succeeded in 等。
How many eggs were you able to get ?你能弄到多少鸡蛋?(不能说:……could you get ?)
I managed to get 10% off the price .我弄了个九折。(不能说:“I could get ……)
After six hours climbing ,we succeeded in reaching the top of the mountain. 经过六小时的攀登,我们终于登上了山顶。(不能说:“……we could reach ……)(指成功地做成)
试比较下列两个句子:he was a terrific liar :he could make anybody believe him .他说起谎来可神啦。能使任何人都相信他。(这里讲的是一般的能力,因此用could 是正确的。)
I talked for a long time, and in the end I managed to make her believe me .我说了老半天,最后才使她相信了我的话。(这里指的是一个具体的场合,不能说:“……I could make her ……)
但是要注意 could 的否定形式 couldn’t 既用来表达一般的能力,也用来表达某一具体的能力。
When I was younger I couldn’t decide what I wanted to do. 我年轻些的时候,不能决定自己想要干什么。
Simon was so drunk that he couldn’t find the front door. 西蒙喝得烂醉,竟找不着正门在哪里。
3、条件句中的could
could 也用于条件句(意思等于 would be able to ).
I could have a really good time if I had a flat of my own. 要是我自己有一套房间,那我就可以过得很快活。
We could do it by midday if we had the tools. 要是我们有工具的话,到中午就可以完成这件工作。
I could break your neck ! 我可以掐断你的脖子。
I could marry him if I wanted to (= I would be able to ……)要是我愿意,我就可以和他结婚。
4、could 和动词不定式完成式连用
有时候,我们需要表达我们有能力做某事件事,但是却没有去做。有一种特殊结构可以表达这个意思:could +不定式完成式(=could have +过去分词)。
I could have married anybody I wanted to .(=I was able to marry anybody ……,but I didn’t .)我本来可以想跟谁结婚就跟谁结婚的。
I could have killed her !(= I was so angry that I was capable of killing her , but I didn’t .)我本来会宰了她的!
You could have helped me !(=you were able to help me –why didn’t you? )你本来可以帮我一把嘛!
这种结构也可用于条件句(意思等于 would have been able to …).
I could have won if I hadn’t fallen over.(= I would have been able to win … )要不是我摔了一跤,我本来是会赢的。
这种结构如果用了否定形式,则表达“即使我尽力而为了,也还是未能做成”。
I couldn’t have won , so I didn't’ go in for the race
反正我也赢不了,所以我就没有参加赛跑
I couldn’t have enjoyed myself more - - it was perfect
我玩得没法再痛快了—简直痛快极了。
关于can 和could, may和might表示可能性的用法:
*Will you answer the phone ? It can be your mother .
*According to the radio it can rain this evening.
这是两个错误的句子,为什么呢?can的用法与may和might 不同。我们用can来谈论更为一般性的或理论上的可能性,而不是某种实际上将要发生或正在发生的可能性。也就是说can通常不用来表示某种实际发生的可能性或真实性。当我们要表达发生某事的实际可能性时,我们用could(或may ,或 might)。因此上述两个句子中的can应当换成could ( may , might)。试比较:
One can travel to Holland by boat ,by hovercraft or by air .到荷兰去,可以乘船,乘气垫船或乘飞机。
I may fly to Amsterdam next week. 我也许下周坐飞机去阿姆斯特丹。
我们不用can来表达某事将会发生的可能性,而是用may或might来表示。
We may go climbing this summer .今年夏天我们可能会去登山。
could 用来表达某事仅仅有发生的可能性,并不表示特别有可能发生。
We could go climbing this summer , but I doubt if we’ll have time.今年夏天我们可能去登山,但是我怀疑我们是否有时间去。
It could rain later this evening. 晚上可能下雨。
may 、 might和could也可以来表示在说话时某事可能是真实的。
You may be right . 可能你是对的。
You could be right ,but I don’t think you are . 可能你是对的,但是我并不认为你是对的。
This could be your big chance.这可能是你的大好机会。
有时候,只在否定句和疑问句中,can 才用来表达现在可能性。
Who can that be at the door ? 门外会是谁呢?
Can it be Susan ? 会不会是苏姗呢?
What can she possibly want?她可能要什么呢?
It can’t be true. 这不可能是真的。
这里就不能说 *It can be Susan或*It can be true 这样的句子。
请注意, can’t这样用,意思与must相反。
It can’t be true. she must be mistaken. 这不可能是真的。她一定是弄错了。
can及could与不定式完成式连用(have+过去分词)都表示对过去某事的猜测。can只能用于疑问句和否定句之中。
Where can she have gone? 她会上哪儿去了呢?
She can’t have gone to school——it’s Saturday. 她不可能是去上学了,今天是星期六。
She could have gone off with some friends . 她可能是和几个朋友一起出去了。(不能说:*she can have…)
could 和不定式完成式连用也表示过去没有实现的可能性:某事可能发生,但是却没有发生。
You were stupid to go skiing there –you could have broken your leg . 你到那个地方去滑雪真傻,你可能会摔断腿的。
It wasn’t a good idea to throw the TV out of the window –it could have hit somebody. 把电视机扔出窗外可不是个好法子—可能会砸着人的。
这种结构也可以用来批评某人没有完成某事。
You could have told me you had invited people to dinner. (= why didn’t you tell me …?)你本来可以告诉我你已请人来吃饭嘛?
如果要表达某事过去不可能,我们可以用“…couldn’t have done…”这种结构。
My parents wanted me to be a doctor , but I couldn’t have put up with all those years of study . 我父母亲原来想让我当医生,但是学习那么多年我可受不了。
和could的用法一样,may和might也可以和不定式完成式连用,表示过去发生某事的可能性。
‘Tom’s very late’—‘He may have missed his train 。’“汤姆这么晚还没起来”。 “他可能误了火车。”
‘What do you think that noise was ?’—‘It might have been a cat. ’“你认为那是什么声音?”—“可能是一只猫”。
might也可以用来表示过去可能发生而没有发生的事情。
You were stupid to try climbing up there .You might have killed yourself . 试图在那里攀登是愚蠢的。你也许会摔死的。
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