Simplify the Expression $( \sqrt { 12 } + \sqrt { 8 } ) ( \sqrt { 12 } - \sqrt { 8 } )$

Multiple Choice

Simplify the expression. Assume all variables represent positive real numbers.
- $( \sqrt { 12 } + \sqrt { 8 } ) ( \sqrt { 12 } - \sqrt { 8 } )$

A) 4
B) $12 + 2 \sqrt { 96 }$
C) 20
D) $12 - 8 \sqrt { 24 }$