Explanation: In AC circuits, the product of volts (voltage) and amperes (current) is known as **apparent power**, measured in Volt-Amperes (VA). This represents the total power delivered by the source. However, not all of this power is used to do useful work due to reactive components (inductance and capacitance) in the circuit. **True power**, measured in Watts (W), is the actual power dissipated by the resistive elements of the circuit, performing useful work. The **power factor** is the factor by which apparent power must be multiplied to obtain true power. It is a dimensionless number between 0 and 1, representing the ratio of true power to apparent power. In other words, True Power = Apparent Power × Power Factor. It's also the cosine of the phase angle between the voltage and current waveforms. * **A) Power factor:** This is correct because it directly defines this relationship. * **B) Apparent power:** This *is* the product of volts and amperes, not the multiplier. * **C) Phase angle:** The phase angle is the angular difference between voltage and current. The *cosine* of the phase angle is the power factor, but the angle itself is not the multiplier.