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': 'Enzyme deficiency in McArdle syndrome \nSelect and explain. \nA. Muscle phosphorylase, B. Liver phosphorylase, C. Liver debranching enzyme, D. Glycogen synthase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Glycogen storage disorderTypeNameEnzyme DeficiencyClinical FeaturesType VMyophosphorylase deficiency,McArdle syndromeMuscle phosphorylasePoor exercise tolerance; muscle glycogen abnormally high(2.5%-4%); blood lactate very low after exerciseRef: Harper&;s Biochemistry; 30th edition; Table 18-2; Chapter 18; Metabolism of Glycogen', 'role': 'assistant'}]