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': 'The tumor which is more commonly located in the tail of the pancreas is: \nSelect and explain. \nA. Glucagonoma, B. Somatostatinoma, C. Gastrinoma, D. Insulinoma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Glucagonomas are usually large tumors at diagnosis. 50-80% occur in the pancreatic tail. Insulinoma distributed equally in the head, body and tail. Gastrinoma is usually located at the gastrinoma triangle in the duodenum. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Pages 3065-67', 'role': 'assistant'}]