Copper
Wood
R.C.C.
Steel
Answer is Right!
Answer is Wrong!
The correct answer is D. Steel.
Cross-arms are structural members that support insulators and conductors on transmission lines. They are typically made of steel, which is a strong and durable material that can withstand the high winds and other forces that can be present on transmission lines.
Copper is a good conductor of electricity, but it is not as strong as steel. Wood is not a good conductor of electricity, and it is also not as strong as steel. R.C.C. is a composite material made of concrete and steel. It is strong and durable, but it is not as good a conductor of electricity as steel.
Therefore, steel is the best material for cross-arms because it is strong, durable, and a good conductor of electricity.