How should the flight attendant’s link be treated when not in use?

The appropriate treatment of a flight attendant's link when not in use is that it must not be left unattended. This policy ensures that critical communication devices are always secure and available for immediate use in case of an emergency or for necessary communication with the flight crew and ground staff. Leaving such a device unattended could potentially lead to unauthorized access or loss of the device, compromising safety protocols. Therefore, maintaining vigilance over communication tools is crucial in the operational environment of a flight.

The other options may suggest actions that could lead to potential security or operational issues, as crew communication is vital for maintaining safety and efficiency.