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': 'Most common functional pancreatic endocrine tumor associated with MEN 1 is: \nSelect and explain. \nA. Zollinger-Ellison syndrome, B. Insulinoma, C. Glucagonoma, D. VIPoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Functional pancreatic endocrine tumor in MEN 1 : 54% develope Zollinger-Ellison syndrome, 18% insulinomas, 3% glucagonomas, 3% VIPomas. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 3060', 'role': 'assistant'}]