英语语法：Past ability & possibility 表现已往的才能&约莫性

In the present tense we use ‘can’ to talk about a general ability – e.g. I can swim – and also for ability at a particular moment – e.g. I can see you! The rules for talking about past abilities are different.如今时态里，我们用can去议论寻常的才能，比如I can swim。另有质貌在一个特定的时间的一种才能，比如I can see you！但议论已往的才能是不同的。

General ability 寻常的才能

We use could to talk about general abilities in the past.

我们用could议论已往寻常的才能。

? He could speak fluent French when he was 5.? I could read before I started school.

Ability on one occasion 某个场合的才能

However, when we talk about ability on one particular occasion, we can’t use could

但是，当我们议论某个特定场合下的才能，我们不克不及用could。

? The burglar was able to get in through the bathroom window.

? The burglar managed to get in through the bathroom window.

We have to use was able to or managed to. We can’t use could.

我们必需用was able to 大概managed to，我们不克不及用could。

? The burglar could get in through the bathroom window.

Ability on one occasion – negative 某个场合的才能—否定式

When we talk about a particular occasion when something wasn’t possible, we can use wasn’t/weren’t able to, didn’t manage to, or couldn’t当我们议论某个特定场合不克不及做某事的才能时，我们用wasn’t /weren’t able to, didn’t manage to, 或是couldn’t

? The burglar wasn’t able to get in through the window.

? The burglar didn’t manage to get in through the window.

? The burglar couldn’t get in through the window.

Hypothetical past ability 假定的已往的才能

Sometimes things were possible in the past but didn’t happen.

偶尔分，我们要形貌在已往约莫会产生但是没有产生的事变。

? I could have gone to university but I decided to get a job.? I would have been able to win the race but I fell over.

We use could have (+ past participle) or would have been able to to talk about these hypothetical events. They can be used in the positive and the negative.我们用could have (+ 已往分词) or would have been able to 来议论这些假定会产生的事变。他们可以是一定式，也可以对否定式。

? I couldn’t have done it without your help.? I wouldn’t have been able to afford it even if it had been for sale.

泉源：英国使馆文明教导处