Of the following outer electronic configurations of atoms,the highest oxidation state is achieved by which one of them

Question

$\begin{array}{1 1}(a)\;(n-1)d^5ns^2\\(b)\;(n-1)d^5ns^1\\(c)\;(n-1)d^3ns^2\\(d)\;(n-1)d^8ns^2\end{array}$