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關(guān)閉窗口 情態(tài)動(dòng)詞can與could的用法歸納
1. 表示能力
(1) 表示現(xiàn)在的能力，用can，如：
He can (=He is able to) swim. 他會(huì)游泳。
He can speak English well. 他英語(yǔ)能說(shuō)得很好。
I can’t remember where I put it. 我記不得把它放在那兒了。
(2) 表示將來(lái)的能力，通常用will / shall be able to，如：
I shall be able to come tomorrow. 明天我能來(lái)。
One day people will be able to go to the moon on holiday. 總有一天人們可以到月球上去度假。
但是，若表示現(xiàn)在決定將來(lái)是否有能力做某事，則可用 can，如：
Can you come to the party tonight？你今晚能來(lái)參加我們的聚會(huì)嗎？
(3) 表示過(guò)去的能力。
① 若泛指過(guò)去的能力，可用could，如：
I could run faster then. 我那時(shí)能跑得更快一些。
②若表示過(guò)去特定場(chǎng)合做某事的能力，則不能用could，而用was / were able to do sth.，或用 managed to do sth，或用 succeeded in doing sth 等。如：
He studied hard and was able to pass the exam. 他學(xué)習(xí)很努力，所以考試能及格。
= He studied hard and managed to pass the exam.
= He studied hard and succeeded in passing the exam.
誤：She could jump into the sea before the ship was blown up. 船爆炸之前，她跳進(jìn)了大海。
正：She was able to jump into the sea before the ship was blown up.
注：在下列情況，could也可表示過(guò)去特定的能力：
①在否定句中，could和was / were able to可通用。如：
I couldn’t / wasn’t able to see him before he left. 他離開之前我沒(méi)有再見(jiàn)到他。
②could與see, hear, smell, taste, feel, understand等表示感知的動(dòng)詞連用時(shí)。如：
I can hear you easily from here. 我在這兒就能很輕易地聽(tīng)到你的話。
Then he spoke slowly, but I could not understand him. 接著他說(shuō)得慢了,但是我聽(tīng)不懂他的話。
③could用在間接引語(yǔ)中時(shí)。如：
He said he could finish the work next week. 他說(shuō)他下周能完成工作。
順便說(shuō)一下，be able to還可用于完成時(shí), 如：
I’m sorry I haven’t been able to come earlier. 對(duì)不起，我沒(méi)有能夠來(lái)得更早一些。
He said he had not been able to answer your letter. 他說(shuō)他一直沒(méi)能給你回信。
2. 表示許可
(1) 對(duì)于現(xiàn)在或?qū)?lái)的許可，用can或could均可，但could 語(yǔ)氣更委婉, 如：
Can / Could I smoke in here? 我可以在這兒吸煙嗎?
You can't pick the ball up in football. 踢足球時(shí)不許可用手持球。
I could come tomorrow if you like. 如果你愿意，明天我可以來(lái)。
② 表示自己允許別人做某事時(shí), 答語(yǔ)應(yīng)用can或may，而不用 could。如：
--Could / Can I use your pen? 我可以借用你的鋼筆嗎?
誤：-- Yes, of course you could. 當(dāng)然可以。
正：--Yes, of course you can / may.
(2) 對(duì)于過(guò)去的許可。 若表示過(guò)去一般性允許用could；表示過(guò)去特定的允許，則不用 could，而需換成其它表達(dá)，如had permission, was / were allowed to。如：
When I lived at home, I could watch TV whenever I wanted to. 我住在家里時(shí), 想什么時(shí)候看電視就什么時(shí)候看。(一般性允許)
I was allowed to see the film yesterday evening. 昨天晚上允許我去看了電影。(特定的允許)
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