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': 'Carcinoid syndrome produces valvular disease primarily involving \nSelect and explain. \nA. Pulmonary valves, B. Tricuspid valves, C. Mitral valve, D. Aortic valve', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]