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: Biochemistry
Which of the following is responsible for the inactive state of Phosphorylase b? 
Select and explain. 
A. Insulin, B. cAMP, C. Calcium, D. ATP
A: Insulin
Answer: A: Insulin 
Explanation: Insulin increases the uptake of glucose leading to the increased formation of glucose 6-phosphate which is an inhibitor of phosphorylase kinase, which in-turn is needed for the activation of Phosphorylase b. Ref: Lippincott's Biochemistry, 5th Edition, Pages 132, 133, 311 ; Harper's Textbook of Biochemistry, 27th Edition, Pages 161, 162, 163