This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pharmacology
[{'content': 'Drug used for both attack as well as prophylaxis of angina: \nSelect and explain. \nA. Isosorbide dinitrate, B. Diltiazem, C. Verapamil, D. Dipyridamole', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. Isosorbide dinitrateIsorbide dinitrate is given for both acute attack as well as prophylaxis of angina, diltiazem is only used for prophylaxis. Dipyridamole worsens angina by coronary steal phenomenon.', 'role': 'assistant'}]