1. Actors (may) MUST learn a lot of dialogues by heart.
2. Your glass is empty. (Must) CAN или MAY I refill it?
3. (Would) MAY I introduce Mr. Brown to you?
4. My sister (can to play) CAN PLAY a few musical instruments.
5. Some years ago I (didn't can speak) DIDN'T SPEAK или COULDN'T SPEAK English.