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': "True in mitral regurgitation (MR) is \nSelect and explain. \nA. Pansystolic murmur at the apex, B. Loud S1, C. Functional or Secondary MR is caused by papillary muscle rupture after myocardial infarction, D. ECG commonly reveals 'P' pulmonale", 'role': 'user'}, {'content': "Answer: A \nExplanation: S1 is soft in MR unlike MS.\xa0\nFunctional or Secondary MR is caused by dilation of the left ventricle causing leakage at the mitral annulus.\xa0\nECG in MR shows 'P'\xa0mitrale due to dilation of the Left atrium.", 'role': 'assistant'}]