Choose the correct alternatives to complete the sentences.
1 My father has to / must wear a suit to work – it’s the dress code in his law firm.
2 You don’t have to / mustn’t check your private inbox during working hours.
3 I’m afraid you should / can drink less coffee because of your high blood pressure.
4 We can’t / don’t have to use a dictionary during the exam.
5 Students can / must leave their bicycles here because it’s forbidden to take them onto the university grounds.