If A is an $\;3 \times 3\;$ non - singular matrix such that $\;A^{'}A=AA^{'}\;$ and $\;B=A^{-1}A^{'}\;$ , then $\;BB^{'} =\;$ :

Question

$(a)\;B^{-1}\qquad(b)\;(B^{-1})^{'}\qquad(c)\;I+ B\qquad(d)\;I$