This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
Drug used for type I and type II Diabetes mellitus is- 
Select and explain. 
A. Glipizide, B. Tolbutamide, C. Metformin, D. Insulin
D: Insulin
Answer: D: Insulin 
Explanation: Uses Of insulin in Diabetes Ref - researchgate.net