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: Pathology
[{'content': 'Calcitonin is a marker of ? \nSelect and explain. \nA. Prostate cancer, B. Medullary carcinoma of thyroid, C. Pheochromocytoma, D. Pancreatic cancer', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Medullary carcinoma of thyroid", 'role': 'assistant'}]