Fill in the gaps with must or mustn't.

1. A teacher to a student: You mustn't talk during the exam. 2. A doctor to a patient: You must stay in bed for three days. 3. A coach to a footballer: You mustn't play football for three weeks. 4. A vet to a dog owner: You mustn't give sweets to your dog. 5. A flight attendant to a passenger: Switch off your phone, please. You mustn't use electronic devices on board an airplane.