What are the two methods to fuel an aircraft?

The correct answer focuses on pressure and gravity fueling, which are two primary methods used to transfer fuel to an aircraft.

Pressure fueling involves using a fuel pump to push fuel into the aircraft's fuel tanks. This method allows for a fast refueling process, which is essential for operations that require quick turnaround times. The pressurized system ensures that the fuel can be effectively dispensed under controlled flow rates, maintaining safety and efficiency.

Gravity fueling, on the other hand, relies on the force of gravity to transfer fuel into the tanks. This method is typically employed when the fuel storage is at a higher elevation than the aircraft, allowing the fuel to flow downward into the tanks. While gravity fueling is generally slower than pressure fueling, it can be useful in situations where power supply may not be available or when dealing with smaller aircraft.

The other options, while they may refer to methods of energy generation or specific fueling scenarios, do not represent the standard practices for fueling aircraft in aviation.