The correct answer is: A. Capacitor run motor.
A capacitor run motor is a single-phase induction motor that uses a capacitor to improve power factor. The capacitor provides a leading current that helps to offset the lagging current of the motor. This results in a more efficient motor that produces less heat.
A shaded pole motor is a single-phase induction motor that uses a shaded pole to create a rotating magnetic field. The shaded pole is a copper ring that is placed around one of the poles of the stator. The current in the stator winding creates a magnetic field. The shaded pole creates a second magnetic field that is out of phase with the first magnetic field. This creates a rotating magnetic field that causes the rotor to turn.
A hysteresis motor is a synchronous motor that uses hysteresis to store energy. The rotor of a hysteresis motor is made of a material that has a high hysteresis loss. When the rotor is turned, it stores energy in the hysteresis losses. This energy is then used to turn the rotor.
A Schrage motor is a synchronous motor that uses a wound rotor. The rotor of a Schrage motor is made of a number of coils that are connected to slip rings. The slip rings allow a variable voltage to be applied to the rotor. This variable voltage creates a rotating magnetic field that causes the rotor to turn.
Capacitor run motors are the most common type of motor that is used for unity power factor. They are relatively inexpensive and easy to maintain. They are also very efficient and produce little heat.