It is often possible to use the present simple or the present perfect:

* I'll come as soon as I finish. or I'll come as soon as I've finished.

* You'll feel better after you have something to eat. or You'll feel better after you've had something to eat.

But do not use the present perfect if two things happen together. The present perfect shows that one thing will be complete before the other (so the two things do not happen together).

Compare:

* When I've phoned Kate, we can have dinner. (= First I'll phone Kate and after that we can have dinner.)

but * When I phone Kate this evening, I'll invite her to the party. (not 'when I've phoned') (In this example, the two things happen together.)

C. After if, we normally use the present simple (if I do/if I see etc.) for the future:

* It's raining hard. We'll get wet if we go out. (not 'if we will go')

* Hurry up! If we don't hurry, we'll be late.

Compare when and if:

We use when for things which are sure to happen:

* I'm going shopping this afternoon. (for sure) When I go shopping, I'll buy some food.

We use if (not 'when') for things that will possibly happen:

* I might go shopping this afternoon. (it's possible) If I go shopping, I'll buy some food.

* If it is raining this evening, I won't go out. (not 'when it is raining')

* Don't worry if I'm late tonight. (not 'when I'm late')

* If they don't come soon, I'm not going to wait. (not 'when they don't come')

@p51

EXERCISES

25.1 Complete these sentences using the verbs in brackets. All the sentences are about the future. Use will/won't or the present simple (I see/he plays/it is etc.).

1. I'll phone (phone) you when I get (get) home from work.

2. I want to see Margaret before she --- (go) out.

3. We're going on holiday tomorrow. I --- (tell) you all about it when we --- (come) back.

4. Brian looks very different now. When you --- (see) him again, you --- (not/recognise) him.

5. We must do something soon before it --- (be) too late.

6. I don't want to go without you. I --- (wait) until you --- (be) ready.

7. Sue has applied for the job but she isn't very well qualified for it. I --- (be) surprised if she --- (get) it.

8. I'd like to play tennis tomorrow if the weather --- (be) nice.

9. I'm going out now. If anybody --- (phone) while I --- (be) out, can you take a message?

25.2 Make one sentence from two.

1. You will be in London again. You must come and see us then.

You must come and see us. when you are in London again.

2. I'll find somewhere to live. Then I'll give you my address.

I --- when ---

3. I'll do the shopping. Then I'll come straight back home.

--- after ---

4. It's going to start raining. Let's go home before that.

--- before ---

5. She must apologise to me first. I won't speak to her until then.

--- until ---

25.3 Read the situations and complete the sentences.

1. A friend of yours is going to visit London. You want to know where she is going to stay.

You ask: Where are you going to stay when _you are in London?_

2. A friend of yours is visiting you. She has to go soon but maybe there's time for a cup of tea.

You ask: Would you like a cup of tea before ---?

3. Your friend is reading the newspaper. You'd like it after her.

You ask: Can I have the newspaper when ---?

4. You want to sell your car. Jim is interested in buying it but he hasn't decided yet.

You ask: Can you let me know as soon as ---?

5. There are serious traffic problems in your town but they are building a new road.

You say: I think it will be better when ---.

25.4 Put in when or if.

1. Don't worry _if_ I'm late tonight.

2. Tom might phone while I'm out this evening. --- he does, can you take a message?

3. I'm going to Rome next week. --- I'm there, I hope to visit a friend of mine.

4. I think Jill will get the job. I'll be very surprised --- she doesn't get it.

5. I'm going shopping. --- you want anything, I can get it for you.

6. I'm going away for a few days. I'll phone you --- I get back.

7. I want you to come to the party but --- you don't want to come, that's all right.

8. We can cat at home or, --- you prefer, we can go to a restaurant.

@p52

Unit 26. Can, could and (be) able to

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 languages?

* 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 languages?

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 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 (could not) is possible in all situations

* We tried hard but we couldn't persuade them to come with us.

* Alf played well but he couldn't beat Jack.

@p53

EXERCISES

26.1 Complete the sentences using can or (be) able to. Use can if possible; otherwise use (be) able to.

1. George has travelled a lot. He _can_ speak four languages.

2. I haven't _been able to_ sleep very well recently.

3. Sandra --- drive but she hasn't got a car.

4. I can't understand Martin. I've never --- understand him.

5. I used to --- stand on my head but I can't do it now.

6. I can't see you on Friday but I --- meet you on Saturday morning.

7. Ask Catherine about your problem. She might --- help you.

26.2 Write sentences about yourself using the ideas in brackets.

1. (something you used to be able to do) I used to be able to sing well.

2. (something you used to be able to do) I used ---

3. (something you would like to be able to do) I'd ---

4. (something you have never been able to do) I've ---

26.3 Complete the sentences with can/can't/could/couldn't + one of these verbs:

come cat hear run sleep wait

1. I'm afraid I _can't come_ to your party next week.

2. When Tim was 16, he was a fast runner. He --- 100 meters in 11 seconds.

3. Are you in a hurry?' 'No, I've got plenty of time. I ---.'

4. I was feeling sick yesterday. I --- anything.

5. Can you speak up a bit? I --- you very well.

6. 'You look tired.' 'Yes, I --- last night,'

26.4 Complete the answers to the questions with was/were able to.

1 A: Did everybody escape from the fire?

B: Yes. Although the fire spread quickly, everybody _was able to escape._

2 A: Did you have difficulty finding Ann's house?

B: Not really. Ann had given us good directions and we ---

3. A: Did you finish your work this afternoon?

B: Yes. There was nobody to disturb me, so ---

4. A: Did the thief get away?

B: Yes. No one realised what was happening and the thief ---

26.5 Complete the sentences using could, couldn't or was/were able to.

1. My grandfather was a very clever man. He _could_ speak five languages.

2. I looked everywhere for the book but I _couldn't_ find it.

3. They didn't want to come with us at first but we _were able to_ persuade them.

4. Laura had hurt her leg and --- walk very well.

5. Sue wasn't at home when I phoned but I --- contact her at her office.

6. I looked very carefully and I --- see a figure in the distance.

7. I wanted to buy some tomatoes. The first shop I went to didn't have any but I --- get some in the next shop.

8. My grandmother loved music. She --- play the piano very well.

9. A girl fell into the river but fortunately we --- rescue her.

10. I had forgotten to bring my camera so I --- take any photographs.

@p54

UNIT 27 Could (do) and could have (done)

A. We use could in a number of ways. Sometimes could is the past of can (see Unit 26C):

* Listen. I can hear something. (now)

* I listened. I could hear something. (past)

But could is not only used in this way. We also in the future (especially to make a suggestion). For example:

* A: What shall we do this evening?

B: We could go to the cinema.

* It's a nice day. We could go for a walk.

* When you go to New York next month, you could stay with Barbara.

* A: If you need money, why don't you ask Karen?

B: Yes, I suppose I could.

Can is also possible in these sentences ('We can go for a walk,' etc.). Could is less sure than can. You must use could (not 'can') when you don't really mean what you say. For example:

* I'm so angry with him. I could kill him! (not 'I can kill him')

B. We also use could to say that something is possible now or in the future:

* The phone is ringing. It could be Tim.

* I don't know when they'll be here. They could arrive at any time.

Can is not possible in these examples (not 'It can be Tim')