The correct answer is: D. All of the above.
The resistance of a conductor is determined by its length, cross-sectional area, and the resistivity of the material it is made of. The longer the conductor, the greater its resistance. The larger the cross-sectional area of the conductor, the lower its resistance. The resistivity of a material is a measure of how difficult it is for electricity to flow through it.
In an armature winding, the resistance of the conductors determines the amount of current that flows through them. The current flowing through the conductors creates a magnetic field. The magnetic field interacts with the stator windings to produce torque. The amount of torque produced depends on the current flowing through the armature windings.
Therefore, the resistance of the armature winding is an important factor in the performance of an electric motor.