A shown in the illustration, which of the lighting fixtures represents an incandescent bulb? EL-0122

Correct Answer: Option D — B

Incandescent bulbs operate by passing current through a tungsten filament until it glows white-hot. Diagram B represents this simple resistive load, which is distinct from the gas-discharge or LED fixtures shown in other figures. These bulbs are commonly used for emergency lighting or specific indicator applications due to their simple, robust design.