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
[{'content': 'Key enzyme in glycogenolysis ? \nSelect and explain. \nA. Branching enzyme, B. Glycogen synthase, C. Debranching enzyme, D. Glycogen phosphorylase', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Glycogen phosphorylase", 'role': 'assistant'}]