What light indicates an above normal EGT reading in addition to the MASTER CAUTION and APU cue lights?

The correct choice indicates that the APU's operational state is being monitored closely. The "HOT" light is specifically designed to signal that the exhaust gas temperature (EGT) is above normal limits for the Auxiliary Power Unit (APU). This warning is crucial because elevated EGT can indicate potential overheating or excessive operational stress on the APU, which could lead to malfunctions or damage if not addressed promptly.

When the "HOT" light illuminates alongside the MASTER CAUTION and APU cue lights, it serves as a clear alert to the pilot that the EGT parameter requires immediate attention. This layered warning system helps ensure pilot awareness of abnormal conditions, allowing for timely intervention before the situation escalates into a more serious issue.

Understanding these indicator lights and their implications is vital for flight crew safety and operational efficacy, particularly in maintaining the integrity of the APU during flight operations.