Change the Radical to Simplest Radical Form $\frac { \sqrt [ 3 ] { 21 } } { \sqrt [ 3 ] { 7 } }$

Multiple Choice

Change the radical to simplest radical form. $\frac { \sqrt [ 3 ] { 21 } } { \sqrt [ 3 ] { 7 } }$

A) $\sqrt [ 3 ] { 3 }$
B) 3
C) $\sqrt [ 3 ] { 14 }$
D) $7 \sqrt [ 3 ] { 21 }$