Rationalize the Denominator and Simplify $\frac { \sqrt { 7 } - \sqrt { 8 } } { \sqrt { 7 } + \sqrt { 8 } }$

Multiple Choice

Rationalize the denominator and simplify. Assume that all variables represent positive real numbers.
- $\frac { \sqrt { 7 } - \sqrt { 8 } } { \sqrt { 7 } + \sqrt { 8 } }$

A) $- 15 - 2 \sqrt { 56 }$
B) $2 \sqrt { 56 } - 15$
C) $15 - 2 \sqrt { 56 }$
D) $15 + 2 \sqrt { 56 }$