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: Physiology
Insulin secretion is decreased by ? 
Select and explain. 
A. Glucogen, B. Gastrin, C. Secretin, D. Somatostatin
D: Somatostatin
Answer: D: Somatostatin 
Explanation: Ans. is 'd' i.e., Somatostatin