Fill in must or must not. 1. You drop litter. 2. You be late. You listen to teachers. 4. You help your parents. 5. You make a noise in transport.

Sure! Here are the sentences filled in with "must" or "must not":

1. You must not drop litter.
2. You must not be late.
3. You must listen to teachers.
4. You must help your parents.
5. You must not make a noise in transport.