85 表示能力或可能性：can/could/be ableto　Track085

（1）表示現(xiàn)在或?qū)?lái)有能力做某事
can表示因?yàn)榫邆淠承┨攸c(diǎn)或條件某人能夠完成某件事，或某事是可能存在的。所以can既表示有能力，也表示可能性。（注意：這里的“可能”與后邊討論的“推測(cè)”是不同的。）
例句
a. Bob can play the piano. He has taken lessons for many years.
（后天獲得的能力）
b. John is strong. He can lift that heavy box. （能力）
c. A fish can’t walk, but it can swim. （天賦的能力）
d. Dogs can bark, but they cannot talk. （天賦的能力）
e. The theater can seat 10,000 people.（可能）
這個(gè)劇院可容納一萬(wàn)人。
f.I can walk to school. It’s not far. （可能）
g. You can see fish at an aquarium（水族館）. （可能）
h. You can buy stamps at the post office, but you can’t buy shoes there.（可能）
注：表示現(xiàn)在有能力做某事，一般不用be able to。
（2）表示過(guò)去有能力做某事
在表示能力時(shí)，could可以作為can的過(guò)去式來(lái)表示過(guò)去有能力做某事。（注意：如果不表示能力，could則不表示過(guò)去。例如could可以表示現(xiàn)在的“許可”“推測(cè)”。）
例句
a. Our son could talk when he was two years old. （表示過(guò)去的能力用can的過(guò)去式could）
b. I could run fast when I was a child, but now I can’t.
c. In those days few workers could support their families.
那時(shí)很少有工人能夠養(yǎng)家糊口。
（3）在表示 “過(guò)去有能力做某事” 時(shí)，could和was/were able to的用法區(qū)別
1）could只能表示過(guò)去“一般的能力，總的能力”。所謂“一般的能力 (general ability)”，即我們?cè)谶^(guò)去想干什么就隨時(shí)可以干什么。（這時(shí)，我們也可用was/were able to。）
例句
a. I could/was able to recite several poems when I was 3 years of age.
我在三歲時(shí)就能背誦幾首詩(shī)。
b. I could/was able to run fast when I was a child, but now I can’t.
小時(shí)候我能跑得很快，但現(xiàn)在不行了。
c. He could/was able to pull down a bull and was acknowledged as a man with superman strength.（我們還可以說(shuō)：He used to be able to…）
他那時(shí)能拉倒一頭牛，被公認(rèn)為是具有神力的人。
2）而要表示在過(guò)去某個(gè)特定場(chǎng)合所表現(xiàn)出的“特定的能力，具體的能力”，或表示某人在某一場(chǎng)合設(shè)法成功地完成了某件事，而非表示泛指的能力時(shí)，我們要用was/were able to。此時(shí)，was/were able to意思相當(dāng)于succeeded in doing或managed to do。
（When used to denote past ability, COULD does not refer to a single instance of ability on a particular occasion, but rather, it signifies an ability in a very general sense. The successful demonstration of ability on a particular past occasion is expressed by means of “be able to”, “manage to ”, “succeed in”,etc.）
下面例句中均不能用could：
a. With the aid of the wood, he was able to swim across the river.
借助那塊木頭，他游到了河的對(duì)岸。
b. I applied everywhere and finally I was able to get a good job.
我到處應(yīng)聘，最后找到了一份好工作。
c. He hurried to the station and was able to catch the train .
他匆匆忙忙趕到車站，趕上了火車。
d. The fire spread through the building quickly but everybody was able to escape. = …everybody managed to escape.
大火很快蔓延到整棟大樓，但是人們還是都逃了出來(lái)。
e. The two boys tried many ways to catch that sly fox and were able to do so at last .
兩個(gè)男孩試用了多種方法去抓那只狡猾的狐貍，終于成功了。
f.Although the pilot was badly hurt he was able to explain what had happened.
盡管飛行員的傷勢(shì)很嚴(yán)重，但是他還是解釋了發(fā)生的一切。
g. Tom has started an exercise program. He was able to run two miles yesterday without stopping or slowing down.
湯姆開(kāi)始了訓(xùn)練計(jì)劃，他昨天跑了兩英里，中途沒(méi)有停也沒(méi)有放慢速度。
3）在否定句中could 和was/were able to可以互換，也就是說(shuō)在否定句中它們就不存在上述區(qū)別了。
例句
a. I applied everywhere but couldn’t get any good job.
b. The fire spread through the building quickly and people couldn’t escape.