What I Can Do A. Remember that the modal MUST is used to express a firm obligation or necessity. DIRECTIONS: Using the situation below, write sentences that express obligation using MUST. Use a separate sheet for your answer. It’s your final examination next week. You have a lot of catching up to do to qualify as one of the honor students. Jot down five things that you must do in preparing for the exams. 1. I must _ 2. I must _ 3. I must _ 4. I must _ 5. I must _ _