The number of terms independent of $x$ in the binomial expansion of $\left(3x^2 + \dfrac{1}{x}\right)^{10}$ is

let m^{th} term is independent of x (here m is integer)

(3x^{2})^{m} x ($\frac{1}{x}$)^{10-m}

x^{2m-10}^{+m}

^{2m-10}^{+m=0}

m=10/3 not integer

Anser : A