Use an Identity to Write the Expression as a Single $2 \cos ^ { 2 } 4 x - 1$

Multiple Choice

Use an identity to write the expression as a single trigonometric function or as a single number.
- $2 \cos ^ { 2 } 4 x - 1$

A) $\frac { 1 } { 2 } \sin 16 x$
B) $\cos 8 x$
C) $\cos 4 x$
D) $2 \sin 4 x$