1) (must/may) i sleep in this room tonight? -yes, you may. 2) (can/should) you say it again? i didn't get what you said. 3) you (must/may) help your parents, they are no longer young.

1) (May) I sleep in this room tonight?-Yes, you may.
2) (Can) you say it again? I didn't get what you said.
3) You (must) help your parents, they are no longer young.

1) May.
2) Can.
3) Must.