Integrate : $\int \sin 4x \cos 4x\;dx$

Question

\[\begin {array} {1 1} (a)\;\frac{1}{16}\cos 8 x +c \\ (b)\;\frac{1}{16}\sin 2 x +c \\ (c)\;\frac{-1}{16}\cos 8 x +c \\ (d)\;\frac{-1}{16}\sin 2 x +c \end {array}\]