Подскажите, пожалуйста! Подчеркните в предложениях модальный глагол или его экв?

Подскажите, пожалуйста! Подчеркните в предложениях модальный глагол или его экв??валент. 1. To become a student of the university you are to pass difficult entrance examinations. 2. A tutor has to help his students to plan their work. 3. If the student fails in an examination, he is allowed to take it again. 4. Students must take examinations at the end of each term.