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: Medicine
[{'content': 'Mild MR.features are \nSelect and explain. \nA. Present in 5-10% population, B. Incidence in low socioeconomic group, C. Presents in 2 years, D. Genetic background Present', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Most people with mitral regurgitation (MR) have no symptoms. People with mild tomoderate MR may never develop symptoms or serious complications Mitral regurgitation (MR), mitral insufficiency, or mitral incompetence, is a form of valvular hea disease in which the mitral valve does not close properly when the hea pumps out blood. It is the abnormal leaking of blood backwards from the left ventricle, through the mitral valve, into the left atrium, when the left ventricle contracts, i.e. there is regurgitation of blood back into the left atrium. MR is the most common form of valvular hea disease.', 'role': 'assistant'}]