Express the Sum or Difference as a Product of Sines $\cos ( 4 \theta ) - \cos ( 6 \theta )$

Multiple Choice

Express the sum or difference as a product of sines and/or cosines.
- $\cos ( 4 \theta ) - \cos ( 6 \theta )$

A) $2 \sin ( 5 \theta ) \sin \theta$
B) $\cos ( - 2 \theta )$
C) $- 2 \cos ( 5 \theta ) \sin \theta$
D) $- 2 \sin ( 5 \theta ) \sin \theta$