What area does the LH MASTER switch supply power to?

The LH MASTER switch is designed to supply power to the LH MAIN and LH ESS buses, which are essential for providing electrical power to various avionics equipment on the left side of the aircraft. This switching mechanism is critical for ensuring that necessary systems remain operational during different phases of flight, especially in situations where power management is crucial for safety and functionality.

The LH MAIN bus typically powers multiple avionics and systems, while the LH ESS bus is dedicated to essential bus functions, which include equipment needed for situations like emergencies. By having the LH MASTER switch control these buses, pilots can help ensure that critical avionics equipment receives the necessary power to function effectively.

The other choices, while they relate to important aircraft systems, are not correct for this specific switch. The emergency lighting is primarily tied to other circuitry designed specifically for illumination during emergencies. The fueling system and hydraulic systems are managed by separate power circuits that do not fall under the purview of the LH MASTER switch, which focuses more on avionics and essential bus functions. Thus, the answer highlights the primary role of the LH MASTER switch in managing avionics power distribution.