The Commutative Property of Addition states that changing the order of the addends does not change the sum. In your provided options, the correct demonstration of the Commutative Property of Addition is:
5z⁹ + 8a = 8a + 5z⁹
This shows that the sum remains the same regardless of the order of the terms being added. The other option, 0 + 5z⁹ = 5z⁹, illustrates the Identity Property of Addition, not the Commutative Property.