Use the Fundamental Identities to Simplify the Expression $\cos ( - x ) \cos x - \sin ( - x ) \sin x$

Use the fundamental identities to simplify the expression.
- $\cos ( - x ) \cos x - \sin ( - x ) \sin x$

A) 2
B) $\cos ^ { 2 } x \sin ^ { 2 } x$
C) 1
D) 0