Grammar Grammar Reference ◆ must - mustn't - can't 4. Read the theory box. Find examples in the leaflet. Explain what they mean. • can't: refusing permission You can't play loud music at night. (You aren't allowed to) 8a • must: obligation You must keep the room clean and tidy. (That's the rule) • mustn't: prohibition You mustn't eat in class. (It's forbidden) 5 1