Which one is the right answer?

B

Step-by-step explanation:

A monomial is a single number or a number multiplied by one or more variables. A sum of monomials is a polynomial.

Since the only thing you can do with variables in a monomial is multiply them by other variables or by numbers, you cannot have a variable in the denominator or a variable in a square root.

Choices A, C, and D have either a variable in a denominator or in a root. That means they are not polynomials.

B