Express the Sum or Difference as a Product $\sin 9 x + \sin 3 x$

Multiple Choice

Express the sum or difference as a product.
- $\sin 9 x + \sin 3 x$

A) $2 \sin 6 x \cos 3 x$
B) $2 \cos 6 x \sin 3 x$
C) $2 \sin 6 x \sin 3 x$
D) $2 \sin 12 x$