Which of the Following Statements Is True of Muscle Glycogen $\alpha$

Multiple Choice

Which of the following statements is true of muscle glycogen phosphorylase?

A) It catalyzes phosphorolysis of the ( $\alpha$ 1 $\rightarrow$ 6) bonds at the branch points of glycogen.
B) It catalyzes the degradation of glycogen by hydrolysis of glycosidic bonds.
C) It degrades glycogen to form glucose 6-phosphate.
D) It exists in an active (a) form and an inactive (b) form that is allosterically regulated by AMP.
E) It removes glucose residues from the reducing ends of the glycogen chains.