6. Sheila simplified an expression using the following steps. Which property justifies Step 3?

Step 1: 5x + 4(3 + 2x)
Step 2: 5x + 12 + 8x
Step 3: 5x + 8x + 12
Step 4: 13x + 12

O A. Identity Property
O B. Associative Property
O C. Distributive Property
D. Commutative Property​