Which expression demonstrates the use of the commutative property of addition in the first step of simplifying the expression open paren negative 1 plus i close paren plus open paren 21 plus 5 i close paren ?

The commutative property of addition lets you switch the order of addends without changing their values. In (−1 + i) + (21 + 5i), moving 21 before i gives −1 + (i + 21) + 5i, which is choice C.

AI-written and checked against the verified answer.