Indicate which property is illustrated in Step 1.

Step 1 5 + (3 + 10) + 0 = 5 + (10 + 3) + 0
Step 2 = (5 + 10) + (3 + 0)
Step 3 = (5 + 10) + 3
Step 4 = 15 + 3
a associative property of multiplication
b commutative property of addition
c identity property of addition
d associative property of addition