Write the Expression in Radical Form $( 7 x + 2 ) ^ { 2 / 7 }$

Multiple Choice

Write the expression in radical form. Assume that all variables represent positive real numbers.
- $( 7 x + 2 ) ^ { 2 / 7 }$

A) $\sqrt [ 7 ] { 7 x ^ { 2 } + 4 }$
B) $( \sqrt [ 7 ] { ( 7 x + 2 ) } ) ^ { 2 }$
C) $\sqrt [ 7 ] { 49 x ^ { 2 } + 4 }$
D) $( \sqrt [ 2 ] { ( 7 x + 2 ) } ) ^ { 7 }$