Simplify the Expression $\sqrt [ 3 ] { \sqrt { 9 } }$

Multiple Choice

Simplify the expression. Assume all variables represent positive real numbers.
- $\sqrt [ 3 ] { \sqrt { 9 } }$

A) 3
B) $\sqrt [ 5 ] { 9 }$
C) $\sqrt [ 3 ] { 3 }$
D) $\sqrt { 3 }$