(b)
We have, $\left( 1 + \omega^{2} \right)^{n} = \left( 1 + \omega^{4} \right)^{n}$
$\Rightarrow \ \ \ \ ( - \omega)^{n} = \left( - \omega^{2} \right)^{n}$
$\Rightarrow \ \ \ \omega^{n} = 1$
$\Rightarrow \ \ \ \ \ \ n = 3$ is least positive value of $n$