Evaluate the Expression $$\left( - \frac { 64 } { 81 } \right) ^ { - 1 / 2 }$$

Multiple Choice

Evaluate the expression.
- $$\left( - \frac { 64 } { 81 } \right) ^ { - 1 / 2 }$$

A) $\frac { 8 } { 9 }$
B) not a real number
C) $- \frac { 9 } { 8 }$
D) $\frac { 32 } { 81 }$