Find the Root $\sqrt [ 4 ] { 16 x ^ { 8 } y ^ { 16 } }$

Multiple Choice

Find the root. Assume that all variables represent nonnegative real numbers.
- $\sqrt [ 4 ] { 16 x ^ { 8 } y ^ { 16 } }$

A) $2 x ^ { 2 } y ^ { 4 }$
B) not a real number
C) $2.497 x ^ { 2 } y ^ { 4 }$
D) $4 \mathrm { x } ^ { 4 } \mathrm { y } ^ { 2 }$