During APU operations, what might be indicated if the LOX QTY LOW message is displayed?

The indication of the LOX QTY LOW message during APU operations signifies that the quantity of liquid oxygen in the system has dropped below a predetermined threshold. This is critical because liquid oxygen is used for the operation of various systems and equipment on the aircraft, often involved with engine start and providing supplemental oxygen for crew and passengers at high altitudes.

When this message appears, it alerts the crew that the liquid oxygen supply may be insufficient for operational needs. This situation requires immediate attention to ensure that the oxygen supply is replenished or appropriate measures are taken to secure the operation of the aircraft, especially concerning safety during flight operations.

The other options suggest conditions that do not pertain to the specific issue related to liquid oxygen quantity, thus reinforcing that the primary concern is indeed the low level of oxygen available.