What is the only valid indication of the status of the autoflight system?

The valid indication of the status of the autoflight system is found in the Flight Mode Annunciators (FMAs) displayed at the top of the Primary Flight Display (PFD). FMAs provide real-time information regarding the operation and status of the autopilot and flight director modes, indicating what the autoflight system is currently doing and what commands it is following. This visibility allows pilots to quickly understand the autopilot's status and make informed decisions during flight.

While the other options provide useful information related to the flight management system or the aircraft's configuration, they do not specifically indicate the operational status of the autoflight system. For instance, FCU settings can show what the pilot intends to set but do not reflect the actual operational state. The MCDU PROG page can provide performance planning data but lacks details about autopilot status, and the EFIS control panel settings pertain more to display configurations than to the operational indications of the autoflight system itself. Thus, FMAs remain the primary and most reliable source for understanding the autoflight system's status.