Write in Radical Form $( \mathrm { mn } ) ^ { 1 / 6 }$

Multiple Choice

Write in radical form. Assume all variables represent positive real numbers.
- $( \mathrm { mn } ) ^ { 1 / 6 }$

A) $\sqrt [ 6 ] { m n }$
B) $( \sqrt { \mathrm { mn } } ) ^ { 6 }$
C) $( \mathrm { mn } ) ^ { - 6 }$
D) $\frac { 1 } { \sqrt [ 6 ] { m n } }$