Which hydraulic systems are normally pressurized by engine driven pumps?

The hydraulic systems of the A320 that are normally pressurized by engine-driven pumps are the Green and Yellow systems. The Green hydraulic system is primarily used for essential flight controls, landing gear, and brakes, while the Yellow hydraulic system provides pressure for various services, including the thrust reversers, brakes, and some flight control surfaces.

The engine-driven pumps are critical because they ensure that these systems are always ready for immediate and reliable operation during flight, taking advantage of the engine's mechanical power. The design of the A320 incorporates multiple hydraulic systems for redundancy and reliability, but the Green and Yellow systems specifically leverage energy from the engines for regular pressurization. This architecture allows for efficient functionality and quick response times during operations.

The other options include systems that do not utilize engine-driven pumps for their primary pressurization. For example, the Blue system is pressurized by an electric pump, which connects to its own power source, thus differentiating its operation significantly from those dependent on engine-driven pumps.