Which expression is the result of the perimeter of rectangle A and demonstrates the closure property?

10x + 4; the answer is a polynomial
2x + 4; the answer is a polynomial
10x + 4; the answer may or may not be a polynomial
2x + 4; the answer may or may not be a polynomial

The expression that is the result of the perimeter of rectangle A and demonstrates the closure property is: 2x + 4; the answer is a polynomial. This is because the sum of the two terms results in a polynomial expression, which is closed under addition.