Correct option is C
Filament lamps, such as incandescent bulbs, operate normally at a power factor of unity (1.0).
This is because they are purely resistive loads, and in resistive circuits, the voltage and current are in phase, resulting in a power factor of 1.0.
There is no reactive component in such circuits, so there is no phase difference between voltage and current.
Resistive Load: Power Factor = 1.0 (Unity)
Inductive Load: Power Factor < 1.0 (Lagging)
Capacitive Load: Power Factor < 1.0 (Leading)
