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': 'Most commonly affected valve in SABE \nSelect and explain. \nA. Pulmonary valve, B. Mitral valve, C. Tricuspid valve, D. Coronary valve', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]