Infinitives with modal verbs

I have no idea how this accident happened. Everyone says it must .......... (cause) by the driver's carelessness.

have been caused

t's astonishing that they should ................. (ask) my that question during my job interview.

have asked

A: How did the burglars manage to escape?

B: Well, the car must ............... (wait) for them outside.

have been waiting

The management might ...................... (plan) to close down some of the branches as they are not competitive.

be planning

A: When Joe said 'He's lazy', do you think he meant me?

B: Well, he could ........... (talk) about someone else, I suppose.

have been talking

I know you want to pay me back but if you are short of money, you needn't .......... (give) it back to me today.

give

Before he learnt to play this piece of music by heart, he must ................ (play) it a hundred times.

have played

A: That coat she was wearing must have been really expensive.

B: Do you think it might ................. (make) of cashemere?

have been made

A: Where is John? He should be here by now.

B: If he's not here, he might ................ (wait) for us in the main hall.

be waiting

A: Where is Mary? I need to talk to her.

B: She's in the attick. She will ................... (water) the pot plants.

be watering

She can't ................. (practise) for an hour; she only began 30 minutes ago.

have been practising

This was not a good place to build a tower like that. It should .............. (build) on more solid ground.

have been built

'Incomprehensible' means something that cannot ................... (understand).

be understood

The dress she was wearing at the Oscar winning ceremony last year must ........... (cost) a fortune!

have cost

When we got home, Harry didn't hear us knock. He must ................ (listen) to loud music.

have been listening

A: When Joe said 'He's lazy', do you think he meant me?

B: Well, he could ........... (talk) about someone else, I suppose.

have been talking

The grammar test we wrote last week couldn't .................. (be) easier.

have been

In my previous office we would ................. (have) lots of fun in the evenings.

have