Simplify the Expression $$\sqrt { \frac { 7 } { 8 } } - \sqrt { \frac { 63 } { 72 } }$$

Multiple Choice

Simplify the expression. Assume all variables represent positive real numbers.
- $$\sqrt { \frac { 7 } { 8 } } - \sqrt { \frac { 63 } { 72 } }$$

A) $- \frac { 1 } { 3 }$
B) -1
C) 0
D) $- 3$