This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Surgery
[{'content': 'Which of the following organs is the most common site of origin of the tumour associated with the Zollinger-Ellison syndrome \nSelect and explain. \nA. Duodenum, B. Lymph nodes, C. Spleen, D. Pancreas', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Gastrin producing endocrine tumour is often found in the duodenal loop,although it also occurs in the pancreas,especially in the head. Bailey & Love ,26th, 1055.', 'role': 'assistant'}]