Simplify by First Converting to Rational Exponents $\sqrt[4]{9 x^{6}}$ A) $\sqrt[x]{3 x^{2}}$

Multiple Choice

Simplify by first converting to rational exponents. Assume that all variables represent positive real numbers.
- $\sqrt[4]{9 x^{6}}$

A) $\sqrt[x]{3 x^{2}}$
B) $3 x^{3}$
C) $\sqrt[4]{9 x^{6}}$
D) $\sqrt{3 x^{3}}$