This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of carbohydrate, Subject name: Biochemistry
[{'content': 'Essential pentosuria is due to deficiency of \nSelect and explain. \nA. Gulonolactone oxidase, B. Phosphoglucomutase, C. Xylulose reductase, D. Fructokinase', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Repeated question', 'role': 'assistant'}]