Which materials are allowable as ground rods according to lightning protection standards?

The correct answer identifies materials that are permissible for use as ground rods in lightning protection systems, which are crucial for safely dissipating lightning strikes into the ground. Copper clad steel, solid copper, and stainless steel are recognized for their excellent conductivity and corrosion resistance, making them suitable choices for grounding applications.

Copper clad steel combines the strength of steel with a layer of copper, ensuring good conductivity while providing structural integrity. Solid copper is well-known for its superior electrical conductivity, making it an ideal material for grounding. Stainless steel, while not as conductive as copper, is resistant to corrosion and can be effective in specific environments.

In contrast, other materials listed in different options do not meet the necessary standards for lightning protection grounding. Aluminum is less preferred due to its tendency to corrode in certain soils and lower conductivity compared to copper. Plastic is non-conductive and cannot be used as a ground rod. Wood, brass, and other metals may lack the desired electrical properties or could corrode, making them unsuitable for grounding purposes.

Hence, the emphasis on copper clad steel, solid copper, and stainless steel as acceptable grounding materials aligns with the requirements set forth in lightning protection standards, ensuring safety and effectiveness in the grounding process.