Simplify the Expression $\frac { \sin ^ { 2 } x - 1 } { \cos ( - x ) }$

Multiple Choice

Simplify the expression.
- $\frac { \sin ^ { 2 } x - 1 } { \cos ( - x ) }$

A) $\cos x$
B) $- \cos x$
C) $- \sin x$
D) $\sin x$