Respuesta :

Answer:

C. (3x^2+4)(x+3)

Step-by-step explanation:

3x^3+9x^2+4x+12

=(3x^3+9x^2)+(4x+12)

=3x^2(x+3)+4(x+3)

=(3x^2+4)(x+3)

Therefore, C. (3x^2+4)(x+3)