Answer:
D
Commutator is the answer
Step-by-step explanation:
The commutator systematically converts the current direction between the rotor and the outer circuit. As the shaft revolves, the commutator converts the course of current in a winding. For a separate armature winding, when a cylinder has reached one-half perfect turn, the winding is now attached so that current passes through it in the reverse of the original direction.