Perform the Indicated Operations $( \sqrt { 13 } + 2 ) ( \sqrt { 13 } - 2 )$

Multiple Choice

Perform the indicated operations. Assume that all variables represent positive numbers.
- $( \sqrt { 13 } + 2 ) ( \sqrt { 13 } - 2 )$

A) 17
B) $13 - 2 \sqrt { 2 }$
C) 11
D) 9