Unit 28 · Modals

must and can't

Study

Study this example:

We use must to say that we believe something is certain:

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You’ve been travelling all day. You must be tired.

(travelling is tiring and you’ve been travelling all day, so you must be tired)

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'Joe is a hard worker.' 'Joe? You must be joking. He doesn’t do anything.'

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Louise must get very bored in her job. She does the same thing every day.

We use can’t to say that we believe something is not possible:

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You’ve just had lunch. You can’t be hungry already.

(we don’t expect people to be hungry immediately after a meal)

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They haven’t lived here for very long. They can’t know many people.

The structure is:

you/she/they (etc.)	must	be (tired / hungry / at work etc.)
	can’t	be -ing (doing / going / joking etc.)
		get / know / have etc.

Study this example:

Martin and Lucy expected their friends to be at home. They rang the doorbell twice, but nobody has answered. Lucy says:

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They must have gone out.

(= there is no other possibility)

For the past we use must have … and can’t have … :

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I lost one of my gloves. I must have dropped it somewhere.

(that’s the only explanation I can think of)

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'We used to live very near the motorway.' 'Did you? It must have been noisy.'

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Sarah hasn’t contacted me. She can’t have got my message.

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Max walked into a wall. He can’t have been looking where he was going.

The structure is:

I/you/he (etc.)	must	have	been (asleep / at work etc.)
	can’t		been -ing (doing / looking etc.)
			gone / got / known etc.

You can use couldn’t have instead of can’t have:

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Sarah couldn’t have got my message.

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Max couldn’t have been looking where he was going.

➜ can’t (‘I can’t swim’ etc.) ➜ Unit 26 ➜ must (‘I must go’ etc.) ➜ Units 31–32 ➜ Modal verbs (can/will etc.) ➜ Appendix 4 ➜ American English ➜ Appendix 7

Exercises (3)

0/3 exercises checked

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28.1

Put in must or can’t.

1
You’ve been travelling all day. You be tired.example
2
That restaurant be very good. It’s always full of people.
3
That restaurant be very good. It’s always empty.
4
I’m sure Kate gave me her address. I have it somewhere.
5
I often see that man in this street. He live near here.
6
It rained every day during their holiday. It have been very nice for them.
7
Congratulations on passing your exam. You be very pleased.
8
This bill be correct. It’s much too high.
9
You got here very quickly. You have driven very fast.
10
Bill and Sue always stay at five-star hotels. They be short of money.
11
Karen hasn’t left the office yet. She be working late tonight.

28.2

Complete each sentence with a verb (one or two words).

1
I’ve lost one of my gloves. I must have it somewhere.example
2
Their house is very near the motorway. It must very noisy.example
3
You’ve lived in this village a long time. You must everybody who lives here.
4
I don’t seem to have my wallet with me. I must it at home.
5
'How old is Ed?' 'He’s older than me. He must at least 40.'
6
I didn’t hear my phone. I must asleep.
7
'You’re going on holiday soon. You must forward to it.' 'Yes, I am.'
8
I’m sure you know this song. You must it before.
9
The road is closed, so we have to go another way. There must an accident.
10
'Do you have a car?' 'You must ! How could I afford to have a car?'
11
David is the managing director of a large company, so he must quite a high salary.

28.3

Use the words in brackets to write sentences with must have and can’t have.

1
We went to our friends’ house and rang the doorbell, but nobody answered. (they / go out)
They out.example
2
Sarah hasn’t contacted me. (she / get / my message)
She my message.example
3
The jacket you bought is very good quality. (it / be / very expensive)
It very expensive.
4
I haven’t seen our neighbours for the last few days. (they / go away)
They away.
5
I can’t find my umbrella. (I / leave / it in the restaurant last night)
I it in the restaurant last night.
6
Amy was in a very difficult situation when she lost her job. (it / be / easy for her)
It easy for her.
7
There was a man standing outside the cafe. He was there a long time. (he / wait / for somebody)
He for somebody.
8
Rachel did the opposite of what I asked her to do. (she / understand / what I said)
She what I said.
9
When I got back to my car, it was unlocked. (I / forget / to lock it)
I to lock it.
10
My neighbours were making a lot of noise in the night. It woke me up. (they / have / a party)
They a party.
11
The light was red, but the car didn’t stop. (the driver / see / the red light)
The driver the red light.
12
Paul has had these shoes for years, but they still look new. (he / wear / them much)
He them much.