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
Oral hypoglycemic which should be stopped prior to surgery under GA: 
Select and explain. 
A. Pioglitazone, B. Metformin, C. Gliclazide, D. Glibenclamide
B: Metformin
Answer: B: Metformin 
Explanation: None