What is a critical rule regarding supply conductors fed from a feeder?

The correct answer highlights an essential safety principle in electrical installations. Supply conductors that are fed from a feeder must not be connected to the grounding conductor or grounding electrodes. This is crucial for maintaining the integrity of the grounding system and preventing potential safety hazards.

When supply conductors are improperly interconnected with the grounding system, it can lead to unintended current paths, which may cause shock hazards or equipment failure. The grounding system is designed to safely carry fault currents away to the ground for protection, while the supply conductors are meant to deliver power without any interruption or interference from grounding systems.

By ensuring that supply conductors remain separate from grounding conductors or electrodes, it helps uphold the safety and reliability of the electrical installation, ensuring that any faults are managed correctly without posing risks to users or electrical equipment.

Other choices suggest different rules that might not apply specifically to the requirement in question. For instance, the connection of supply conductors to grounding systems serves different purposes and should follow distinct regulations, which is why option B stands out clearly as the most critical rule in this context.