Which of the following expressions are not polynomials?

(i) $\mathrm{x}^{2}+2 \mathrm{x}^{-2}$ is not a polynomial because $-2$ is the power of variable $\mathrm{x}$ is not a non negative integer.

(ii) $\sqrt{a x}+x^{2}-x^{3}$ is not a polynomial because $\frac{1}{2}$ is the power of variable $x$ is not a non negative integer.

(iii) $3 \mathrm{y}^{3}-\sqrt{5} \mathrm{y}+9$ is a polynomial because the powers of variable $\mathrm{y}$ are non negative integers.

(iv) $\mathrm{ax}^{\frac{1}{2}}+\mathrm{ax}+9 \mathrm{x}^{2}+4$ is not a polynomial because $\frac{1}{2}$ is the power of variable $\mathrm{x}$ is not a non negative integer.

(v) $3 \mathrm{x}^{-2}+2 \mathrm{x}^{-1}+4 \mathrm{x}+5$ is not a polynomial because $-2$ and $-1$ are the powers of variable $\mathrm{x}$ are not non negative integer $s$.