Final answer:
The symbol represents a lit round bulb in a schematic diagram. Therefore, the correct option is B.
Step-by-step explanation:
In schematic diagrams, the symbol stands for a lit round lightbulb and functions as a common representation for a lightbulb emitting light inside a circuit. Schematic diagrams give engineers and technicians a clear, globally known visual language by using symbols to represent different components.
The illustration of a lit lightbulb indicates that it is in the operational state; it communicates the existence of an electrical circuit that is active and the lightbulb's emission. These symbols improve communication and circuit documentation clarity and efficiency in electrical engineering and related domains.
Therefore, the correct option is B.