7A GRAMMAR BANK - Past modals

must/might/may/can’t/couldn’t + have + past participle

1. I must have left my phone at Anna’s. I definitely remember having it there.

You must have seen something. You were there when the accident happened.

2. Somebody might have stolen your wallet when you were getting off the train.

He still hasn’t arrived. I may not have given him the right directions.

3. She can’t have gone to bed. It’s only ten o’clock!

You can’t have seen their faces very clearly. It was too dark.

- We use must/ may/ might/ can’t + have + past participle to make deductions or speculate about past actions.

1. We use must have when we almost sure that something happened or was true.

The opposite of must have is can’t have – see 3 below NOT mustn’t have

2. We use might/ may have when we think it’s possible that something happened or was true. We can also use could have with this meaning, e.g. Somebody could have stolen your wallet when you were getting off the train.

3. We use can’t have when we are almost sure something didn’t happen or that it is impossible. We can also use couldn’t have when the speculation is about the distant past, e.g. You couldn’t have seen their faces very clearly, e.g. She couldn’t have gone to bed. It’s only ten o’clock.

should have/ ought to have + past participle

We’ve gone the wrong way. We shouldn’t have turned left at the traffic lights.

It’s my fault. I ought to have told you earlier that my mother was coming.

- Use should have + past participle to say that somebody didn’t do the right thing, or to express regret or criticism.

- You can use ought to have as an alternative to should have, e.g. I ought to have told you earlier.

Ex. a

I’m certain I left my umbrella at home. It’s not in the office.

I must have left my umbrella at home.

1. Holly’s crying. Perhaps she’s had an argument with her boyfriend.

She might have had an argument with her boyfriend.

2. I’m sure Ben has read my email. I sent it first thing this morning.

Ben must have read my email.

3. I’m sure Sam and Ginny haven’t got lost. They have satnav in their car.

Sam and Ginny can’t have got lost.

4. You saw Ellie yesterday? That’s impossible. She was in bed with flu.

You can’t have seen Ellie yesterday.

5. Perhaps John didn’t see you. That’s why he didn’t say hello.

John might not have seen you.

6. I’m sure Lucy has bought a new car. I saw her driving a blue VW Golf!

Lucy must have bought a new car.

7. I’m sure Alex wasn’t very ill. He was only off work for one day.

Alex can’t have been very ill.

8. They didn’t come to our wedding. Maybe they didn’t receive the invitation.

They might not have received the invitation.

9. This tastes very sweet. I’m sure you used too much sugar.

You must have used too much sugar.

10. It definitely wasn’t my phone that rang in the cinema. Mine was on silent.

It can’t have been my phone.

Ex. b

A. We couldn’t understand anybody in Paris.

B. You should have learnt some French before you went.

A. Sue is  in bed with a stomach ache.

B. She oughtn’t to have eaten so much chocolate cake yesterday.

1. A. Tom told me the date of his party, but I’ve forgotten it.

B. You should have written it down.

2. A. I was late because there was so much traffic.

B. You oughtn’t to have come by car. The metro is much faster.

3. A. Amanda was rude to everyone at my party.

B. You shouldn’t have invited her. You know what she’s like.

4. A. I don’t have any money left after going shopping yesterday.

B. You oughtn’t to have bought so many shoes. Did you really need three pairs?

5. A. You look really tired.

B. I know. I should have gone to bed earlier last night.

6. A. The chicken’s still frozen solid.

B. I know. You ought to have taken it out of the freezer earlier.

7. A. I think I’ve burnt my face.

B. I’m not surprised. You shouldn’t have sat in the sun all afternoon without any sunscreen.