Choose the correct options

Children(don't have to/have to/mustn't) put on their hats. It's warm outside.

1. You [have to|don't have to|mustn't]leave class before the bell. It's a strict rule.
2. You [have to|don't have to|mustn't]help if you are tired. You need some rest.
3. The meal is a treat. You [have to|don't have to|mustn't] buy it.
4. My train is leaving in ten minutes. I [don't have to|have to|must]go now.
5. My classmates [have to|don't have to|mustn't]go by bus to school. They live quite far from it.
6. If the traffic light is red you [have to|don't have to|must]stop and wait.
7. Animals in the zoo [have to|don't have to|mustn't]hunt for food.