What should the electrical firing unit not be in during its inspection?

The correct selection emphasizes that during the inspection of an electrical firing unit, it should not be in arm status. The arm status indicates that the firing system is ready to launch fireworks, thereby presenting a risk of unintentional discharge during inspection. When inspecting safety-critical equipment such as firing systems, it is paramount to ensure that all components are in a safe and non-operational state to prevent any accidental activation.

In contrast, being in active mode or test status would also create a potential safety concern, but they imply different operational conditions that can sometimes be controlled during testing. Thus, while these statuses have their respective procedures, the critical point is that the unit must never allow firing readiness (arm status) during inspection to maintain safety protocol. Disarm status is indeed safe for inspection as it ensures that the unit is not ready to fire.