The correct answer is C. kVAR.
Power factor correction is the process of improving the power factor of an electrical system. The power factor is a measure of how efficiently an electrical system is using power. A power factor of 1 indicates that the system is using power efficiently, while a power factor of less than 1 indicates that the system is wasting power.
Capacitors can be used to improve the power factor of an electrical system by providing reactive power. Reactive power is the component of power that is not used to do work. Capacitors provide reactive power by storing and releasing energy. This helps to balance the load on the electrical system and improve the power factor.
The capacity of a capacitor bank is expressed in kVAR. This is because capacitors provide reactive power, which is measured in kVAR. The kVAR rating of a capacitor bank is determined by the amount of reactive power that the bank needs to provide to improve the power factor of the system.
The other options are incorrect because they are not units of reactive power. kW is a unit of real power, kVA is a unit of apparent power, and volts is a unit of voltage.