What is the main function of a fuel system in an aircraft?

The primary function of a fuel system in an aircraft is to supply fuel to the engine for combustion. This involves several complex processes that ensure the engine receives the correct type and amount of fuel necessary for optimal performance. The fuel system includes components such as fuel tanks, pumps, valves, lines, and injectors, all of which work together to deliver fuel from the tank to the engine under varying conditions of demand and altitude.

While the other options may involve functions related to the fuel system, their roles do not encompass the central purpose of fuel systems in aircraft operations. Cooling the engine is typically achieved through dedicated cooling systems, while filtering impurities is a supplementary function to ensure the fuel's cleanliness, not its primary role. Measuring fuel volume is also important for determining fuel quantity but does not define the main action of the fuel system. Therefore, option B accurately reflects the essential role of the fuel system in supporting engine operation through combustion supply.