*Note: A polynomial is an expression having variables and coefficients, that involves only the operations of addition, subtraction, multiplication, and non-negative integer exponents of variables

and is not a polynomial because it does not contain integer power of the variable “y”

And, is not a polynomial because it contains a negative power of the variable, which is not the criteria for a polynomial.

∴ y is a polynomial as it follows the criteria of polynomial and all the other do not follow these criteria.

Hence, option C is correct