Which unit is used to select units for the Auto Flight System?

The EFIS Control Panels are the correct choice for selecting units for the Auto Flight System on the A320. These panels allow the flight crew to configure and modify display settings related to the aircraft's navigation data and flight parameters. The EFIS (Electronic Flight Instrument System) enables the pilots to choose between various measurement units, including metric or imperial systems, for different flight parameters, enhancing situational awareness and ensuring that the information presented aligns with the crew's preferences and operational requirements.

The other options do not play a role in selecting units for the Auto Flight System. The Master Caution/Warning Lights are notification systems that alert the crew to specific issues or malfunctions but do not have any functionality related to unit selection. Standby Flight Instruments provide essential flight data in case of primary instrument failure, but they also lack the capability to adjust or select units. The Landing Gear System is focused on the operation and status of the landing gear, unrelated to the configuration of flight data units.