20 POINTS MARKING BRAINLEIST IF QUICK AND RIGHT

Answer/Step-by-step explanation:
[D]
Polynomials will be closed under an operation if the operation produces another polynomial. When multiplying polynomials, the variables' exponents are added, according to the rules of exponents.
(Note: exponents in polynomials are whole numbers.)
[RevyBreeze]
Question:
Polynomials are closed under multiplication. What does that mean?
Answer: When you multiply polynomials, the result is always a polynomial.