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
Key enzyme in glycogenolysis ? 
Select and explain. 
A. Branching enzyme, B. Glycogen synthase, C. Debranching enzyme, D. Glycogen phosphorylase
D: Glycogen phosphorylase
Answer: D: Glycogen phosphorylase 
Explanation: Ans. is 'd' i.e., Glycogen phosphorylase