The correct answer is: A. Steel cored aluminium
Steel cored aluminium (ACSR) is a composite material used for overhead transmission lines. It is made up of a central core of steel surrounded by an outer layer of aluminium. The steel core provides strength and rigidity, while the aluminium provides conductivity. ACSR is a popular choice for overhead transmission lines because it is strong, lightweight, and corrosion-resistant.
Galvanized steel is a type of steel that has been coated with a layer of zinc. The zinc coating protects the steel from corrosion, making it a good choice for use in outdoor applications. However, galvanized steel is not as strong as ACSR, and it is not as good a conductor of electricity.
Cadmium copper is a type of copper that has been alloyed with cadmium. The cadmium makes the copper more resistant to corrosion, but it also makes it more brittle. Cadmium copper is not a good choice for use in overhead transmission lines, because it is not as strong as ACSR and it is not as good a conductor of electricity.
Therefore, the correct answer is ACSR.