Write the Expression as the Sine, Cosine, or Tangent of an Angle

Multiple Choice

Write the expression as the sine, cosine, or tangent of an angle.
- $\cos 7 x \cos 4 x - \sin 7 x \sin 4 x$

A) $\sin 11 x$
B) $\sin 3 x$
C) $\cos 11 \mathrm { x }$
D) $\cos 3 x$