Simplify Assume All Variables Represent Positive Real Numbers $\sqrt [ 3 ] { \frac { 7 } { 3 } }$

Multiple Choice

Simplify. Assume all variables represent positive real numbers.
- $\sqrt [ 3 ] { \frac { 7 } { 3 } }$

A) $\frac { 63 } { 3 }$
B) $\frac { \sqrt [ 3 ] { 63 } } { 3 }$
C) $\frac { \sqrt [ 3 ] { 189 } } { 3 }$
D) $\frac { \sqrt [ 3 ] { 21 } } { 3 }$