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: Pharmacology
[{'content': 'Drug of choice for Zollinger Ellison syndrome: \nSelect and explain. \nA. Proton pump inhibitor, B. Antacids, C. Antithistminics, D. H2 blockers', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Proton pump inhibitor', 'role': 'assistant'}]