Which one is polynomials NOT closed under?

A. Addition

B. Subtraction

C. Multiplication

D. Division

If one polynomial had equation P = x^2 + 2 and a second polynomial had equation Z = x^3 - 3, then when you find the quotient of P and Z, you get a variable term of 1/x. 1/x cannot be a term in a polynomial.

Polynomials are NOT closed under the operation of division. (D)