The glycogen debranching enzyme is required for

the transfer of 3-glucose units from one branch to another.
the transfer of phosphate from one position to another.
cleaving alpha (1 to 6) sugar linkages
a and c
a, b and c

A and C

A. the transfer of 3-glucose units from one branch to another.

C. cleaving alpha (1 to 6) sugar linkages

Explanation:

Glycogenolysis Enzymes

Two enzymes participate in glycogenolysis:

Glycogen phosphorylase, which catalyzes phosphorolysis or phosphorolytic cleavage of alpha 1-4 glycosidic bonds, which consists of the sequential separation of glucose residues from the non-reducing end, depending on the reaction:

(glucose) n + Pi3 ← → (glucose) n-1 + glucose-1-P

This reaction is very advantageous for the cell, compared to one of hydrolysis.

Glycogen debranching enzyme.

Glycogen phosphorylase cannot cleave O-glycosidic bonds in alpha (1-6). The glycogen de-branching enzyme has two activities: alpha (1-4) transferase glycosyl that transfers each unit of trisaccharide to the non-reducing end, and eliminates branching by alpha 1-6 glycosidic bonds:

glucose-6-P + H2O2 → glucose + Pi