A. We use can to say that something is possible or that somebody has the ability to do something. * We use can + infinitive (can do/can see etc.): * We can see the lake from our bedroom window. * Can you speak any foreign language? * I can come and see you tomorrow if you like.
The negative is can't (= cannot): * I'm afraid I can't come to the party on Friday.
B. (Be) able to ... is possible instead of can, but can is more usual: * Are you able to speak any foreign language? But can has only two forms, can (present) and could (past). So sometimes it is necessary to use (be) able to... Compare: * I can't sleep. but I haven't been able to sleep recently. (can has no present perfect) * Tom can come tomorrow.
but Tom might be able to come tomorrow. (can has no infinitive)
C. Could and was able to... Sometimes could is the past of can. We use could especially with:
see hear smell taste feel remember understand
* When we went into the house, we could smell something burning. * She spoke in a very low voice, but I could understand what she said.
We also use could to say that somebody had the general ability or permission to do something: * My grandfather could speak five languages. * We were completely free. We could do what we wanted. (= we were allowed to do ...)
We use could for general ability. But if we are talking about what happened in a particular situation, we use was/were able to... or managed to... (not could):
* The fire spread through the building quickly but everybody was able to escape. or ... everybody managed to escape. (but not 'could escape') * They didn't want to come with us at first but we managed to persuade them. or ... we were able to persuade them. (but not 'could persuade')
Compare: * Jack was an excellent tennis player. He could beat anybody. (He had the general ability to beat anybody) but * Jack and Alf had a game of tennis yesterday. Alf played very well but in the end Jack managed to beat him. or ... was able to beat him. (= he managed to beat him in this particular game)
The negative couldn't (could not) is possible in all situations: * My grandfather couldn't hear what she was saying over the telephone. * We tried hard but we couldn't persuade them to come with us. * Alf played well but he couldn't beat Jack.
Exercise 1: Complete the sentences using can or (be) able to. Use can if possible; otherwise use (be) able to. 1. Sandra ___________ drive but she hasn't got a car. 2. I can't understand Martin. I've never __________ understand him. 3. I used to _________ stand on my head but I can't do it now. 4. I can't see you on Friday but I ____________ meet you on Saturday morning. 5. Ask Catherine about your problem. She might __________ help you.
Exercise 2: Complete the sentences with can/can't/could/couldn't + one of these verbs:
come do hear run sleep wait
1. When Tim was 16, he was a fast runner. He ______ 100 meters in 11 seconds. 2. Are you in a hurry?' 'No, I've got plenty of time. I ________.' 3. I was feeling sick yesterday. I _____________ anything. 4. Can you speak up a bit? I ____________ you very well. 5. 'You look tired.' 'Yes, I _____________ last night,'
Exercise 3: Complete each phrases:
1. I can____________________ in just a minute. 2. I could do it better if __________________ 3. I'll be able to do______________
Allan: Mary, can you help me with the filing please?
Mary: Wish I could but I'm tied up right now. I have to finish sending these documents to our clients. Allan: Do you think you'll be able to help me this afternoon then?
Mary: If I'll be able to finish this before lunch, maybe I could help you with that
1. What are your greatest dreams in life? Why? 2. What are your talents? 3. What are the things you can do that other people can't? 4. Can you cook?? What kinds of food? 5. Can you drive and repair a car?
