Simplify the Radical Expression $\sqrt [ 4 ] { \sqrt [ 5 ] { x y } }$

Multiple Choice

Simplify the radical expression. Write the answer in radical form when appropriate.
- $\sqrt [ 4 ] { \sqrt [ 5 ] { x y } }$

A) $\sqrt [ 20 ] { x y }$
B) $\sqrt [ 5 ] { x y }$
C) $\sqrt [ 40 ] { x y }$
D) $\sqrt [ 4 ] { x y }$