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: Pathology
[{'content': 'Zollinger Ellison syndrome is caused by ? \nSelect and explain. \nA. Gastrin secreting tumor, B. Somatostatin secreting tumor, C. CCK secreting tumor, D. Adrenalin secreting tumor', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Gastrin secreting tumor Zollinger-Ellison syndrome is caused by gastrin-secreting tumors. These gastrinomas are most commonly found in the small intestine or pancreas.", 'role': 'assistant'}]