For expression to be polynomial all the exponent must be non negative.
For first option,
![(2)/(x)-8y=2x^(-1)-8y](https://img.qammunity.org/2023/formulas/mathematics/college/mc732bxsi2106n945zvyw8zkzrkdhavht1.png)
It is not a polynomial expression.
For second option
![3x^2-7y](https://img.qammunity.org/2023/formulas/mathematics/college/b6lgwm4k8lxv4lwlzidqul7r4p7t913j6x.png)
No negative exponent, so it is polynomial equation.
For third option,
![4x^2-9](https://img.qammunity.org/2023/formulas/mathematics/high-school/yf2nbvtwpoj5tcfnc3h42yjl6muph54nll.png)
No negative exponent, so it is polynomial equation.
For fourth option,
![3x^(-2)+y^3](https://img.qammunity.org/2023/formulas/mathematics/college/y65zpfykijo6k8rqjjspy1hwg9x6022etb.png)
It is not a polynomial expression.
So option B and C is correct option.