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': 'The first heart sound is loud in all the following except \nSelect and explain. \nA. Mitral stenosis, B. Anemia, C. Thyrotoxicosis, D. Mitral valve calcification', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]