3 Choose the correct answer.
1 Helen hasn't arrived yet. She mustn't I can't have
got a lift from her mum.
2 Where's my phone? I might / might not have
left it on the bus.
3 The cinema could / must have been full. There
were no tickets left.
4 Jack can't/might have finished his homework.
He hasn't had enough time.
5 That was a strange noise. It may I can have been
the kids next door.