The correct answer is D.
To reverse the direction of rotation of a capacitor start motor while it is running, you need to reverse the direction of current flow through the auxiliary winding. This can be done by reversing the connections of the auxiliary winding to the power supply.
If you disconnect the motor from the supply and then reconnect it with the reversed connections of the main winding, the motor will not start. This is because the main winding is a single-phase winding, and the direction of current flow through it does not affect the direction of rotation of the motor.
If you reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply, the motor will start in the opposite direction. However, this is not a safe way to do it, as there is a risk of the motor starting in the wrong direction and causing damage.
Therefore, the safest and most effective way to reverse the direction of rotation of a capacitor start motor while it is running is to reverse the direction of current flow through the auxiliary winding by reversing the connections of the auxiliary winding to the power supply.