Write in Radical Form $( 7 x ) ^ { 1 / 5 }$

Multiple Choice

Write in radical form. Assume all variables represent positive real numbers.
- $( 7 x ) ^ { 1 / 5 }$

A) $- \sqrt [ 5 ] { 7 x }$
B) $\frac { \sqrt { 7 x } } { 5 }$
C) $\sqrt [ 1 / 5 ] { 7 x }$
D) $\sqrt [ 5 ] { 7 x }$