If the transmission voltage of a line increases, then the volume of the conductor material required :

Correct option is A

If the transmission voltage of a line increases then the volume of the conductor material required decreases.

$$v = \frac{P^2 \rho \ell^2}{V^2 \cos^2 \phi W} \\\boxed{v \propto \frac{1}{V^2}} \\\text{Where,} \\v = \text{volume of material} \\V = \text{Transmission voltage}$$​