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
Which of the following antidiabetic drugs can cause vitamin B12 deficiency? 
Select and explain. 
A. Glipizide, B. Acarbose, C. Metformin, D. Pioglitazone
C: Metformin
Answer: C: Metformin 
Explanation: Lactic acidosis (more with phenformin) and megaloblastic anemia (more with metformin) due to vitamin B12 defi­ciency are the major adverse effects of these drugs. Lactic acidosis is more likely to occur in the presence of hepatic and renal impairment or alcohol ingestion.