Simplify the Radical Expression $\sqrt [ 20 ] { x ^ { 4 } }$

Multiple Choice

Simplify the radical expression. Write the answer in radical form when appropriate.
- $\sqrt [ 20 ] { x ^ { 4 } }$

A) $\sqrt [ 5 ] { \frac { 1 } { x } }$
B) $\sqrt [ 4 ] { x }$
C) $\sqrt [ 16 ] { x }$
D) $\sqrt [ 5 ] { x }$