D. the armature and commutator      Â
Explanation:
An electric generator is based on the principle that when a conducting coil rotates in the magnetic field, an electric current is generated. Â It converts mechanical energy to electrical energy.
Armature is the rotating part of the generator. Armature is connected to commutator which is a cylindrical in shape and rotates with it. It also connects the armature to the external circuit by brushes. Â