Evaluate the Logarithm $\log _ { 6 } ( - 6 )$

Evaluate the logarithm. $\log _ { 6 } ( - 6 )$

A) 0
B) $\frac { 1 } { 6 }$
C) -1
D) $e^ { - 1 }$
E) $\log _ { 6 } ( - 6 )$ is undefined.