Why is it crucial for the electrical system to function properly when the APU is operating?

The electrical system's proper functioning is essential to support APU function requirements. The Auxiliary Power Unit (APU) relies on the electrical system to provide power for its operations, including starting the APU, controlling various components, and ensuring that it can supply power to other aircraft systems when necessary. This interdependence means that if the electrical system is not functioning adequately, the APU may not operate effectively, which can affect the overall performance of the aircraft during ground operations and ensure adequate support for onboard systems.

The other options, while potentially relevant in different contexts, do not directly pertain to the primary functions that the APU must perform. Fuel efficiency monitoring, cabin comfort, and remote access are important aspects of aircraft operation, but they do not directly influence the immediate functional requirements of the APU itself. Thus, the focus on supporting APU function requirements underscores the critical role the electrical system plays in the APU's operation.