Decide Whether the Expression Is or Is Not an Identity $\sin \theta$

Multiple Choice

Decide whether the expression is or is not an identity.
-Find $\sin \theta$ if $\cot \theta = - 2$ and $\cos \theta < 0$ .

A) $\frac { \sqrt { 5 } } { 5 }$
B) $- \frac { 1 } { 2 }$
C) $\frac { \sqrt { 5 } } { 2 }$
D) $- 5$