If the $r^{th}$ term in the expansion of $(\large\frac{x}{3}-\frac{2}{x^2})^{10}$ contains $x^4$ then $r$ is equal to

Question

$\begin{array}{1 1}(A)\;4\\(B)\;3\\(C)\;2\\(D)\;\text{none of these}\end{array}$