To determine whether the given expression is a polynomial, recall that a polynomial is the sum of two or more monomials. A monomial is either a number, a variable, or an expression that is the product of one or more variables. Additionally, monomials can only have non-negative integer exponents. Consider the given expression. Since monomials cannot contain variables in the denominator, the third term in the above expression is not a monomial. Therefore, the given expression is not a polynomial.