What must they do in these situations? write questions and answers using must or mustn't. use the following phrases call a doctor buy a present call the firemen help him find his way home stay up late go to bed early example: he is always late for school. what must he do? he must get up earlier. 1. maxim is going to a birthday party today. 2. sam is ill. 3. my brother is going to leave very early tomorrow. 4. a man sees a house on fire. 5. you see a crying child lost in the street.