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
Enzymes not used in glycogen metabolisma) Glycogen phosphorylase Bb) Glycogen synthase Ic) Glycogen synthase Cd) Glycogen synthase A 
Select and explain. 
A. ab, B. ad, C. bd, D. bc
D: bc
Answer: D: bc 
Explanation: Glycogen synthase 1 & Glycogen synthase C