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': 'Oral hypoglycemic which should be stopped prior to surgery under GA: \nSelect and explain. \nA. Pioglitazone, B. Metformin, C. Gliclazide, D. Glibenclamide', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]