The correct answer is B) By reversing the armature-interpole-compensating winding leads as a unit. In a cumulatively compounded DC motor with interpoles and compensating windings, the direction of rotation is determined by the interaction between the magnetic fields produced by the armature, series field, and interpole windings. To reverse the direction of rotation, the entire set of armature, interpole, and compensating windings must be reversed as a unit, as these windings work together to produce the motor's torque. Reversing only the armature winding leads (option A) or the series field winding leads (option C) would not correctly reverse the direction of rotation. Reversing the shunt field winding leads (option D) would also not reverse the direction, as the shunt field does not directly affect the torque production.