This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'A 59 year old man with severe myxomatous mitral regurgitation is asymptomatic, with a left ventricular ejection fraction of 45% and an end systolic diameter index of 2.9 cm/m2. The most appropriate t/t is \nSelect and explain. \nA. Mitral valve repair or replacement, B. No treatment, C. ACE inhibitor therapy, D. Digoxin and diuretic therapy', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]