Exercise 1Choose the correct form of can, could, be able lớn (affirmative or negative). Use a khung of be able to only if a form of can or could is not possible.
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8 Yesterday I lost my keys and I looked for them everywhere, but I couldn"twasn"t able tocan"t find them.
We use can/could to describe ability, and we use can’t/couldn’t to lớn describe absence of ability.She could play the piano very well.Children can’t concentrate for long periods of time.I can speak Chinese.Possibility
We also use can to talk about possibility.Anyone can win this competition. All the participants are very good. I can’t come khổng lồ the tiệc ngọt next week.Permission
We use can/could to talk about something that is or was allowed và we use can’t/couldn’t to talk about something that is not allowed.You can’t smoke in the house, but you can smoke in the terrace if you want.
We also use can to ask for permission.Can I come in?Requests
We us can/could in requests, i.e. When we ask somebody to vày something.Can you help me?Could you speak more slowly, please?see, smell, hear, feel, taste
Verbs of perception (see, smell, hear, etc.) are stative verbs & cannot be used in a continuous form. Instead, we use can.Can you hear that? (NOT Are you hearing that?)I can smell gas! (NOT I’m smelling gas!)
be able to
Be able to is often similar to can and we may use it instead of can to lớn talk about ability. But be able to is more formal & is not as common.They are able to lớn do the job faster than anyone else.
But can only has present and past forms: can–could. For all other verb forms (infinitive, gerund, present perfect, etc.) we should use be able to.I haven’t been able to study for the exam. (present perfect)I’d lượt thích to be able to talk khổng lồ her more often. (to-infinitive; NOT khổng lồ can)I don’t like loud music in pubs. I like being able lớn talk with my friends. (-ing form)Will we be able lớn talk lớn the singer after the concert? (infinitive)
can/could vs be able to
We can use can và be able to to talk about general ability in the present.She can speak five languages. She’s able khổng lồ speak five languages.
We can use could & be able to lớn talk about general ability in the past.My son could walk when he was 11 months old.My son was able to walk when he was 11 months old.
But if we want to lớn say that someone did something in a specific situation, we must use was/were able to, or managed to + infinitive.There was a fire in the office but all the workers were able to/managed to escape. (NOT could escape)He lost his maps but after driving around for a long time, he was able to/managed to lớn find the place. (NOT could find)
In negative sentences, both could and be able to can be used to lớn say that we were not capable of doing something on a specific occasion.It was very dark and they couldn’t find the exit.