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 important investigation for diagnosis of Zollinger Ellison-syndrome is - \nSelect and explain. \nA. Ca++ infusion test, B. Secretin injection test, C. ACTH stimulation test, D. Steroid assay', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]