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: Surgery
[{'content': 'Serum calcitonin is a marker for \nSelect and explain. \nA. Anaplastic carcinoma, B. Papillary carcinoma, C. Medullary carcinoma, D. Follicular carcinoma', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]