What pilot action is required for an APU fire on the ground?

For an APU fire on the ground, the appropriate pilot action is to follow the ECAM procedure, as indicated in the correct answer. The ECAM (Electronic Centralized Aircraft Monitor) provides critical guidance and checklists for managing various aircraft emergencies, including an APU fire.

When an APU fire is detected, the system automatically initiates an APU shutdown and fire extinguishing sequence. This automation is designed to rapidly respond to the threat and minimize risk to the aircraft and crew, highlighting the A320's advanced safety features. By following the ECAM instructions, pilots can ensure that they execute the necessary steps promptly and effectively, which may include activating fire extinguishing systems or shutting down other aircraft systems as required.

While other options may pertain to APU operations, they do not address the immediate and critical actions required in response to a fire situation. For example, turning the APU start switch ON or the bleed switch ON would not be appropriate during a fire. Pushing the APU fire AGENT switch is part of the procedure as well, but following the entire ECAM is crucial to ensure that all safety protocols are observed and that appropriate measures are taken to manage the situation.