Simplify Assume That Variables Represent Positive Real Numbers $$\sqrt [ 4 ] { - 81 x ^ { 8 } y ^ { 12 } }$$

Multiple Choice

Simplify. Assume that variables represent positive real numbers.
- $$\sqrt [ 4 ] { - 81 x ^ { 8 } y ^ { 12 } }$$

A) $- 81 x ^ { 2 } y ^ { 8 }$
B) not a real number
C) $- 3 x ^ { 2 } y ^ { 3 }$
D) $- 3 x ^ { 4 } y ^ { 8 }$