3 Complete the sentences with can, must or mustn't.

1. You've finished your chores, so you **can** watch TV now. 2. Turn off the tap. We **must** save water. 3. **Can** I borrow a book from your bookcase, please? 4. The sink is dirty. I **must** clean it. 5. You **must** tidy your drawer. It's very messy. 6. Be careful with that mirror. You **mustn't** break it.