What type of brakes are available with only a green hydraulic failure?

In the case of a green hydraulic failure on the A320, the airplane utilizes alternate brake systems, which are designed to maintain aircraft safety and control in the event of normal brake system failures. These alternate brakes are different from standby brakes, as they are intended for use when there's a loss of the primary hydraulic system.

The correct choice indicates that alternate brakes function with antiskid capability, which is critical for maintaining traction and preventing wheel lockup during braking. This is especially important during diverse operational scenarios, such as wet or slippery runway conditions, where maintaining control over the aircraft is crucial.

In contrast, the other options do not reflect the functionality that is specifically available during a green hydraulic failure. Standby brakes are generally used in scenarios involving total hydraulic failure or when crew intervention is needed to activate them. Alternate brakes without antiskid could lead to increased risk during braking, and accumulator brakes typically serve as a temporary measure, lacking antiskid functionality and therefore are not used as a primary solution in this context. Thus, the capability of the alternate brakes to include antiskid under a green hydraulic failure ensures enhanced braking performance and safety.