Complete the Sentence So the Result Is an Identity $2 \sin 8 x \sin 17 x$

Multiple Choice

Complete the sentence so the result is an identity. Let x be any real number.
- $2 \sin 8 x \sin 17 x$

A) $\sin 25 x + \sin 9 x$
B) $\frac { 1 } { 2 } ( \cos 25 x + \cos 9 x )$
C) $\cos 25 x + \cos 9 x$
D) $\cos 9 x - \cos 25 x$