The correct answer is: A. pony motor.
A pony motor is a small motor that is used to start a larger motor. It is connected to the larger motor by a clutch, and when the pony motor is started, it turns the larger motor until it reaches a speed where it can start on its own.
A D.C. compound motor is a type of motor that has both a D.C. field winding and a D.C. armature winding. The D.C. field winding is used to create a magnetic field, and the D.C. armature winding is used to create a current. The current in the armature winding creates a magnetic field that opposes the magnetic field of the field winding. This opposition creates a torque that starts the motor.
Providing damper winding is a method of starting a synchronous motor by connecting a set of windings to the rotor. These windings are connected to a capacitor, and when the motor is started, the current in the windings creates a magnetic field that opposes the magnetic field of the stator. This opposition creates a torque that starts the motor.
However, the most common and efficient way to start a synchronous motor is by using a pony motor.