$\cos ^4 A - \sin ^4 A =$

Question

$\begin{array}{1 1}(A) \; 2 \cos ^2 A+1 \\(B)\; 2 \cos ^2 A -1 \\(C)\;2 \sin ^2 A -1 \\(D)\;2 \sin ^2 A +1 \end{array}$