Simplify the Radical Expression $\sqrt[4]{81 x^{8}}$ A) 324
B) $3 x^{2}$ C) $-3 x^{2}$

Multiple Choice

Simplify the radical expression. Assume all variables represent nonnegative real numbers.
- $\sqrt[4]{81 x^{8}}$

A) 324
B) $3 x^{2}$
C) $-3 x^{2}$
D) $9 x^{2}$