What are the four general types of fuel quantity gauges?

The correct answer highlights four different gauges used for monitoring fuel quantity, each serving a specific function and operating on distinct principles.

The sight glass is a clear tube or container that allows for a visual inspection of fuel levels; it provides an immediate and straightforward visual assessment of fuel quantity. Mechanical gauges use moving parts driven by fuel level to indicate the quantity, relying on physical mechanisms like floats or levers. Electrical gauges function by utilizing sensors, such as resistive or capacitive elements, to provide a readout of fuel levels electronically. Electronic gauges represent a more advanced technology that not only provides accurate fuel readings but can also interface with onboard systems for enhanced monitoring and reporting.

By including mechanical, electrical, and electronic types, the answer encompasses the broader spectrum of traditional and modern fuel measurement technologies used in aircraft fuel systems. Other options may include combinations of these types, but option B distinctly lists four that span both classic and contemporary methods of fuel level assessment.