Modal verbs

Task:Choose the appropriate verb.

They can/ might be away for the weekend but I'm not sure.
You may/might leave now if you wish.
Could/May you open the window a bit, please?
He can/could be French, judging by his accent.
May/Can you play the piano?
Listen, please. You may not/might not speak during this exam.
They can't/may not still be out!
You couldn't/might not smoke on the bus.
With luck, tomorrow can/could be a sunny day.