The correct answer is: A. induction motors
Induction motors are the most common type of motor used in industry. They are simple, reliable, and relatively inexpensive. However, they also have a relatively low power factor. This is because they draw a large amount of reactive current, which does not contribute to the actual power output of the motor.
Synchronous motors have a higher power factor than induction motors. This is because they do not draw any reactive current. However, they are more expensive than induction motors and are not as widely used.
Single phase motors are the simplest type of motor. They are used in many small appliances, such as fans and vacuum cleaners. They have a very low power factor, which is why they are not used in large industrial applications.
D.C. motors have a power factor of 1. This is because they do not draw any reactive current. However, they are not as efficient as induction motors and are not used in large industrial applications.
In conclusion, the primary reason for low power factor in a supply system is due to the installation of induction motors.