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
Muscle phosphorylase deficiency leads to which glycogen storage disorder 
Select and explain. 
A. Hers disease, B. McArdles disease, C. Cori's disease, D. Andersen disease
B: McArdles disease
Answer: B: McArdles disease 
Explanation: Muscle phosphorylase deficiency leads to McArdle's disease. (Mnemonic "M for M') which is characterised by poor exercise tolerance, Muscle glycogen being abnormally high and blood lactate level very low after exercise.
Mnemonic

Heri's disease - Hepatic phosphorylase
Andersen disease - Branching enzyme
Cori's disease - Debranching enzyme.