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': 'Which vitamin is associated with glycogen phosphorylase? \nSelect and explain. \nA. Pyridoxin, B. Niacin, C. Riboflavin, D. Thiamine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pyridoxin Pyridoxal phosphate is an essential cofactor for glycogen phosphorylase', 'role': 'assistant'}]