Find the Root $- \sqrt [ 4 ] { 256 x ^ { 12 } y ^ { 8 } }$

Multiple Choice

Find the root. Assume that all variables represent nonnegative real numbers.
- $- \sqrt [ 4 ] { 256 x ^ { 12 } y ^ { 8 } }$

A) $6.233 x ^ { 3 } y ^ { 2 }$
B) $- 4 x ^ { 3 } y ^ { 2 }$
C) $16 x ^ { 3 } y ^ { 2 }$
D) not a real number