This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
[{'content': 'A 43-year-old woman is diagnosed with mitral valve stenosis. During physical examination the first heart sound is abnormally loud. Which of the following heart valves are responsible for the production of the first heart sound? \nSelect and explain. \nA. Aortic and mitral, B. Aortic and tricuspid, C. Tricuspid and mitral, D. Mitral and pulmonary', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The first heart sound is caused by the closure of the tricuspid and mitral valves. The second heart sound is caused by the closure of the aortic and pulmonary valves.', 'role': 'assistant'}]