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
Enzyme deficiency in McArdle syndrome 
Select and explain. 
A. Muscle phosphorylase, B. Liver phosphorylase, C. Liver debranching enzyme, D. Glycogen synthase
A: Muscle phosphorylase
Answer: A: Muscle phosphorylase 
Explanation: 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