You are answering a USMLE-style medical question. Question: A 38-year-old woman presents to her physician’s clinic for recurrent episodes of chest pain that wakes her from her sleep. While usually occurring late at night, she has also had similar pains during the day at random times, most recently while sitting at her desk in her office and at other times while doing the dishes at home. The pain lasts 10–15 minutes and resolves spontaneously. She is unable to identify any common preceding event to pain onset. The remainder of her history is unremarkable and she takes no regular medications. She works as an accountant. There is no history of smoking or drug use, however, she does consume 5 alcoholic drinks per week. Examination reveals: pulse 70/min, respirations 16/min, and blood pressure 120/70 mm Hg. A physical examination is unremarkable. Which of the following would be effective in reducing her symptoms? Options: A) Aspirin B) Isosorbide dinitrate C) Heparin D) Propranolol Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.