What should be included in performing proper maintenance of a D.C. motor's commutator?

Correct Answer: Option D — side-cutting the copper segments and undercutting the mica

Proper commutator maintenance requires undercutting the mica insulation slightly below the copper segment surface and side-cutting or chamfering segment edges. This prevents mica high-spots from lifting brushes, which causes arcing and rapid wear per IEEE 45 guidelines.