What is the complete factorization of the polynomial below?
x3 + 2x2 + 4x + 8
A. (x+ 2)(x + 2)(x+ 21)
B. (x-2)(x + 2)(x-21)
C. (x-2)(x+ 2)(x+21).
D. (x + 2)(x+21)(x - 2)