Operation of a switch or GFCI shall not cause loss of what?

The correct answer is that the operation of a switch or Ground Fault Circuit Interrupter (GFCI) shall not cause loss of primary power. Primary power refers to the main source of electrical energy that feeds into a system, such as the electrical service panel of a building. Ensuring that the operation of a switch or a GFCI does not lead to the loss of primary power is crucial for maintaining the overall functionality and safety of the electrical system.

The operation of devices like GFCIs is specifically designed to protect against electrical shock hazards by interrupting the flow of electricity when a ground fault is detected. While these devices may deactivate certain circuits for safety reasons, they should be designed in a manner that allows for essential power sources, such as lights, outlets, or life safety systems, to remain functional. This is particularly important in emergency situations where loss of primary power could lead to dangerous conditions.

In contrast, other options point to variations of circuits or power that might not have the same critical importance for operational continuity. Maintaining primary power ensures that all essential systems remain operational, while secondary power, back-up power, and additional circuits can potentially be sacrificed for safety without undermining the core function of the electrical system.