Choose the One Alternative That Best Completes the Statement or Answers

Multiple Choice

Choose the one alternative that best completes the statement or answers the question.
Solve the equation.
- $$9 ^ { x } = \frac { 1 } { 729 }$$

A) $\{ - 3 \}$
B) $\{ 3 \}$
C) $\left\{ \frac { 1 } { 3 } \right\}$
D) $\left\{ - \frac { 1 } { 3 } \right\}$