Use Identities to Fill in the Blank with the Appropriate $\cos \theta$

Multiple Choice

Use identities to fill in the blank with the appropriate trigonometric function name.
-Find $\cos \theta$ if $\tan \theta = 4$ and $\sin \theta < 0$ .

A) $- 17$
B) $\frac { 1 } { 4 }$
C) $- \frac { \sqrt { 17 } } { 17 }$
D) $- \frac { \sqrt { 17 } } { 4 }$