Which property of addition is shown below?
a+bi+c+di=a+c+bi+di
a. identity property
b. associative property
c. commutative property
d. inverse property

a. commutative property

Because community property means that you can move or change (commute) the order of the numbers without modifying the result of the sum.

In this case you are commuting bi and c, because bi + c = c + bi.

When you only change the order of the numbers is an addition you are using commutative property.

For more information, if  you had doubts about it could be the associative property, discard it because associative property is refering to grouping the numbers, which is not the case.

Commutative, this property allow moving terms without changing the result