Use Radical Notation to Write the Expression $\left( 81 x ^ { 6 } \right) ^ { 1 / 2 }$

Multiple Choice

Use radical notation to write the expression. Simplify if possible.
- $\left( 81 x ^ { 6 } \right) ^ { 1 / 2 }$

A) $9 \sqrt [ 3 ] { x }$
B) $9 x ^ { 6 }$
C) $9 x ^ { 3 }$
D) $81 x ^ { 3 }$