Select the correct answer.

What is the completely factored form of this polynomial?
x3 + 3x2 − 6x − 18
A.
(x − 2)(x − 3)(x + 3)
B.
(x2 − 6)(x + 3)
C.
(x2 + 3)(x − 6)
D.
(x + 6)(x − 1)(x + 3)