Select the Function That Is Equivalent To $f(x)=\cos 7 x-\cos 17 x$

Multiple Choice

Select the function that is equivalent to $f(x) =\cos 7 x-\cos 17 x$ .

A) $f(x) =2 \cos 12 x \sin 5 x$
B) $f(x) =-2 \cos 12 x \sin 5 x$
C) $f(x) =-2 \sin 12 x \sin 5 x$
D) $f(x) =2 \cos 12 x \cos 5 x$