Workers on the assembly line produce 4x + 6 boats each day. Which expression shows how many boats they produced in 12 days?
A12(4x + 6)
B12(4x) + 6
C12 4x+6
D4x+6 12
A12(4x + 6)
B12(4x) + 6
C12 4x+6
D4x+6 12