Answer:
The answer is option C. Closure
Explanation:
The closure property of addition for polynomials states that the result of adding two polynomials will always be another polynomial.
Therefore, the property of polynomial addition that says that the sum of two polynomials is always a polynomial is the closure property.
Polynomials are closed under addition, as when polynomials are added, the letters and their exponents do no change, we just add the coefficients of the like terms. Hence, the result will also be a polynomial.