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.
- $\cos \frac { \pi } { 7 } \cos \frac { \pi } { 11 } + \sin \frac { \pi } { 7 } \sin \frac { \pi } { 11 }$

A) $\sin \frac { 18 \pi } { 77 }$
B) $\cos \frac { 4 \pi } { 77 }$
C) $\sin \frac { 4 \pi } { 77 }$
D) $\cos \frac { 18 \pi } { 77 }$