Помогите пожалуйста найти инфинитив и определить его форму и функцию! Умоляю!

Помогите пожалуйста отыскать инфинитив и найти его форму и функцию! Упрашиваю! Спасибо.
1. To grant pardon is the prerogative of the Crown.
2. They must have been arrested over a year ago.
3. The victim is the first person to be interviewed.
4. He seems to be investigating a criminal case.
5. A student must pass a group of examinations to obtain a law degree.
6. The aim of the preliminary investigation is to draw up an indictment.