Which hydraulic system(s) provides pressure for the NORMAL brakes?

The hydraulic system responsible for providing pressure to the NORMAL brakes on the A320 is the Green system. The Green hydraulic system is primarily dedicated to essential functions such as the normal braking system, landing gear operation, and some other critical components. In particular, the normal brakes utilize pressurized fluid from the Green hydraulic system to operate effectively and safely.

While the A320 has three hydraulic systems (Green, Blue, and Yellow), the normal brakes specifically rely on the Green system. The Yellow system does have a role in braking, but it is reserved for alternate braking operations or situations where the Green system is unavailable. The Blue system primarily supports the operation of the thrust reversers and other non-braking functions.

Therefore, the Green hydraulic system is the correct answer as it directly supplies the required pressure for the NORMAL brakes in normal operating conditions, ensuring that brake performance is optimal during standard operations.