Wybierz prawidłowe uzupełnienie zdań.

1 I’m not sure where the car keys are, but they could be/must be in one of the drawers.
2 The woman we met last night can’t have been/must have been Monika’s mother because they all have dark hair and her hair was red.
3 There must have been/must be a solution to this problem, but I’m really tired, so I’ll think about it tomorrow.
4 I’m sure it was Sally’s car that we saw. It must be/must have been her car because it had exactly the same stickers on the windows.
5 The train is running late, so we might not arrive/could arrive on time. But, perhaps we’ll make it.