C Underline the correct item. 15. Ann may/has to leave school early tomorrow. She has a dentist appointment after school. 16. If Ben gets permission from his parents, he may/must study in France next year. 17. Kate should have/ must have studied a lot for the history exam. He got very high mark. 18. Students mustn't/needn't run in the school corridors. It's against the rules. 19. You can/must raise your hand and wait before you ask a question.