c
$E = \frac{{iR}}{L} = \frac{{i.\rho }}{A} = \frac{{neA{v_d}\rho }}{A}$ $ \Rightarrow $ ${v_d} \propto E$ (Straight line)
$P = {i^2}R = {\left( {\frac{{EA}}{\rho }} \right)^2}R$ $ \Rightarrow $ $P \propto {E^2}$ (Symmetric parabola)
Also $P \propto {i^2}$ (parabola)
Hence all graphs $a, b, d$ are correct and $c$ is incorrect.