A. Study this example:
We use
must to say that we feel sure something is true:
* 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.)
* 'Jim
is a hard worker.' 'Jim? A hard worker? You must be joking. He's very lazy.'
* Carol
must get very bored in her job. She does the same thing every day.
We use
can't to say that we feel sure something is not possible:
* You've
just had lunch. You can't be hungry already. (People are not normally hungry
just after eating a meal. You've just eaten, so you can't be hungry.)
* Brian
said he would definitely be here before 9.30. It's 10 o'clock now and he's
never late. He can't be coming.
* They
haven't lived here for very long. They can't know many people.
Study
the structure:
I/you/he
(etc.) must/can't be (tired/hungry/at work etc.)
I/you/he
(etc.) must/can't be (doing/coming/joking etc.) do/go/know/have etc.
I/you/he
(etc.) must/can't do/go/know/have etc.
B. For
the past we use must have (done) and can't have (done). Study this example:
George
is outside his friends' house.
He has
rung the doorbell three times but nobody has answered.
They
must have gone out. (otherwise they would have answered)
* The
phone rang but I didn't hear it. I must have been asleep.
* I've
lost one of my gloves. I must have dropped it somewhere.
* Jane
walked past me without speaking. She can't have seen me.
* Tom
walked straight into a wall. He can't have been looking where he was going.
Study
the structure:
I/you/he
(etc.) must/can't have been (asleep/at work etc.)
I/you/he
(etc.) must/can't have been (doing/working etc.)
I/you/he
(etc.) must/can't have done /gone/known/had etc.
Couldn't
have ... is possible instead of can't have...:
* She
couldn't have seen me.
* Tom
couldn't have been looking where he was going.
EXERCISES
28.1 Put
in must or can't.
1.
You've been travelling all day. You must be very tired.
2. That
restaurant --- be very good. It's always full of people.
3. That
restaurant --- be very good. It's always empty.
4.
You're going on holiday next week. You --- be looking forward to it.
5. It
rained every day during their holiday, so they --- have had a very nice time.
6.
Congratulations on passing your exam. You --- be very pleased.
7. You
got here very quickly. You --- have walked very fast.
8. Bill
and Sue go away on holiday very often, so they --- be short of money.
28.2
Complete the sentences with a verb in the correct form.
1. I've
lost one of my gloves. I must have dropped it somewhere.
2. They
haven't lived here for long. They can't know many people.
3. Ted
isn't at work today. He must --- ill.
4. Ted
wasn't at work last week. He must --- ill.
5. (The
doorbell rings) I wonder who that is. It can't --- Mary. She's still at work at
this time.
6. Carol
knows a lot about films. She must --- to the cinema a lot.
7. Look.
Jack is putting on his hat and coat. He must --- out.
8. I
left my bike outside the house last night and this morning it isn't there any
more. Somebody must --- it.
9. Ann
was in a very difficult situation. It can't --- easy for her.
10.
There is a man walking behind us. He has been walking behind us for the last 20
minutes. He must --- us.
28.3
Read the situations and use the words in brackets to write sentences with must
have and can't have.
1. The
phone rang but I didn't hear it. (I/asleep)
_I must
have been asleep._
2. Jane
walked past me without speaking. (she/see/me)
_She
can't have seen me._
3. The
jacket you bought is very good quality. (it/very expensive)
4. I
haven't seen the people next door for ages. (they/go away)
5. I
can't find my umbrella. (I/leave/it in the restaurant last night)
6. Don
passed the exam without studying for it. (the exam/very difficult)
7. She
knew everything about our plans. (she/listen/to our conversation)
8. Fiona
did the opposite of what I asked her to do. (she/understand/what I said)
9. When
I woke up this morning, the light was on. (I/forget/to turn it off)
10. The
lights were red but the car didn't stop. (the driver I see/the red light)
11. I
was woken up in the middle of the night by the noise next door. (the
neighbours/have/a party)
the answer
28.1
2
must 3 can't
4
must 5 can't
6
must 7 must 8 can't
28.2
3 be
4 have
been
5 be
6 go or
have been
7 be
going
8 have
taken/have stolen
9 have
been
10 be
following
28.3
3 It
must have been very expensive.
4 They
must have gone away.
5 I must
have left it in the restaurant last night.
6 The
exam can't have been very difficult.
7 She
must have been listening to our conversation./She must have listened to.
8 She
can't have understood what I said.
9 I must
have forgotten to turn it off.
10 The
driver can't have seen the red light.
11 The
neighbours must have been having a party.
