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': 'A biopsy from a mass shows parafollicular cells.\nWhat is the tumor marker? \nSelect and explain. \nA. Calcitonin, B. T4, C. Thyroxine, D. Thyroglobulin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Caclitonin is the tumor marker for MTC which arises from parafollicular cells.', 'role': 'assistant'}]