Convert the Expression to Radical Notation $x ^ { 1 / 7 }$

Multiple Choice

Convert the expression to radical notation.
- $x ^ { 1 / 7 }$

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