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: Physiology
True about insulin is 
Select and explain. 
A. Anabolic steroid, B. Induce lipolysis, C. Produced by a-cells, D. None
D: None
Answer: D: None 
Explanation: Insulin is a polypeptide hormone, secreted by b cells in the islets of Langerhans, which promotes glucose use, protein synthesis, and the formation and storage of neutral lipids; available in various preparations including genetically engineered human insulin, which is currently ored. Insulin is used parenterally in the treatment of diabetes mellitus.Ref: Ganong&;s review of medical physiology;24th edition; page no-432