Explanation: A power transformer's primary winding is an inductive load. Inductive loads inherently cause the current to lag behind the voltage, resulting in a poor, lagging power factor. By placing a capacitor in series with the primary, its capacitive reactance, which causes current to lead voltage, can counteract the transformer's inductive reactance. This action brings the total circuit current and voltage closer into phase, effectively improving the power factor (making it closer to 1). This reduces the reactive power drawn from the source, making the load appear more resistive. Option B is incorrect because voltage regulation refers to the stability of the output voltage under varying load conditions, which is primarily determined by the transformer's internal design and impedance, not a series power factor correction capacitor. Option C is incorrect; a capacitor does not rectify AC into DC; that function requires diodes.