When will the evaporator blowers be on?

The correct choice highlights that the evaporator blowers will be activated when the AVIONICS MASTER switch is in the ON position. This is crucial because the evaporator blowers are part of the environmental control system, which is essential for maintaining the proper operational environment in the cockpit and avionics systems. The activation of the blowers helps to ensure that electronic equipment operates within safe temperature limits, thereby preventing overheating and ensuring reliability during flight.

The function of the evaporator blowers to engage with the AVIONICS MASTER switch prioritizes the protection and functionality of critical flight systems, so that the crew has a stable and safe environment to manage the aircraft effectively. Understanding this relationship highlights the importance of integrating various systems to ensure safety and efficiency within the aircraft's operations.