The electronic configuration of gadolinium is

Question

$\begin{array}{1 1}(a)\;[Xe]4f^85d^96s^2&(b)\;[Xe]4f^75d^16s^2\\(c)\;[Xe]4f^35d^56s^2&(d)\;[Xe]4f^65d^26s^2\end{array}$