If $x\textgreater0$, which of the following is equivalent to $\sqrt[3]{x^{4}}$ ?  $ $ $I. x+x^{\frac{1}{3}}$  $ $ $II. \left(x^{\frac{1}{3}}\right)^{4}$  $ $ $III. x^{2}\left(x^{-\frac{2}{3}}\right)$ 
选项为:A:None  B:$I$ and $II$ only  C:$II$ and $III$ only  D:$I$, $II$, and $III$  请回答其中一个选项.