Evaluate the Expression $$\left( - \frac { 49 } { 36 } \right) ^ { - 1 / 2 }$$

Multiple Choice

Evaluate the expression.
- $$\left( - \frac { 49 } { 36 } \right) ^ { - 1 / 2 }$$

A) $\frac { 7 } { 6 }$
B) $- \frac { 6 } { 7 }$
C) $\frac { 49 } { 72 }$
D) not a real number