This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Acute coronary syndrome, Subject name: Medicine
[{'content': 'Which drug prolongs life in a patient with chronic stable angina? \nSelect and explain. \nA. Aspirin, B. Beta Blocker, C. CCB, D. ACE inhibitor', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Due to oxygen conservation capability, beta blockers have been proved to reduce moality in CSA. Multiple RCT have shown benefit of beta blockers', 'role': 'assistant'}]