Complete with: must, mustn't or can't. 1. Please don't make so much noise. We....... wake the children. 2. There isn't much time. We.... hurry. 3. You cook your meals in the room. It isn't allowed. 4. You wear a seatbelt when you are in a car. That's the rule. 5. You put posters in the room. It's forbidden.

Here are the completed sentences with explanations: 1. Please don't make so much noise. We **mustn't** wake the children. *Explanation:* We use *mustn't* to indicate prohibition or something that is not allowed. Since we don't want to wake the children, we are prohibited from making noise. 2. There isn't much time. We **must** hurry. *Explanation:* We use *must* to indicate obligation or necessity. Since there isn't much time, it's necessary to hurry. 3. You **can't** cook your meals in the room. It isn't allowed. *Explanation:* We use *can't* to indicate that something is not allowed. In this case, it's not permitted to cook meals in the room. 4. You **must** wear a seatbelt when you are in a car. That's the rule. *Explanation:* We use *must* to indicate obligation. Wearing a seatbelt is obligatory and a rule. 5. You **mustn't** put posters in the room. It's forbidden. *Explanation:* We use *mustn't* to indicate prohibition. It's forbidden to put posters in the room.