What is the product of 3x(x2 + 4)?
A=x2 + 3x + 4
B=3x3 + 4
C=3x3 + 12x
D=3x2 + 12x
A=x2 + 3x + 4
B=3x3 + 4
C=3x3 + 12x
D=3x2 + 12x