This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
[{'content': 'Pheochromocytoma may be associated with: \nSelect and explain. \nA. Medullary carcinoma of the thyroid, B. Papillary carcinoma of the thyroid, C. Anaplastic carcinoma of the thyroid, D. Follicular carcinoma of the thyroid', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. Medullary carcinoma of the thyroidMEN 2a: Sipple syndromeMEN 2ba. Thyroid; Medullary thyroid carcinomaa. Thyroid: Medullary thyroid carcinomab. Pheochromocytomab. Pheochromocytomac. Parathyroid hyperplasiac. Mucosal neuromas and Marfanoid appearance', 'role': 'assistant'}]