Подчеркните в каждом из них модальный глагол или его эквивалент.
1) Good citizens must learn to perform their duties and exercise their civil rights.
2) When children don’t listen to reason, their parents have to exercise authority.
3) What is your problem? I may be able to help you.
4) The conference is to be held next month.
5) You should find the work that suits you best.