A metal underground gas pipe cannot be used as which type of grounding device?

A metal underground gas pipe cannot be used as an electrode for grounding purposes primarily due to safety and code compliance reasons. An electrode is a grounding component that provides a path for electrical current to safely divert to the ground in the event of a fault or surge.

Underground gas pipes are not specifically designed or intended for grounding applications. Using them as electrodes could introduce hazards, such as compromising the integrity of the gas pipe or creating pathways for electrical faults that could lead to dangerous situations, including gas leaks or explosions. Additionally, grounding practices are governed by electrical codes, which often specify that only designated grounding electrodes—like ground rods, concrete-encased electrodes, or other approved metallic systems—be used for grounding.

In contrast, the other options listed pertain to electrical systems and components that are either designed for grounding use (like conductors and connectors) or can be safely employed in specific grounding applications (like grounding straps), ensuring compliance with safety standards and maintaining system functionality.