Which of the following is a polynomial with roots 2, 3i, and -3i?
A. f(x) = x^3 - 2x^2 + 6x - 9
B. f(x) = x^3 - 6x ^2 + 9x - 18
C. f(x) = x^3 - 6x^2 + 18x - 2
D. f(x) = x^3 + 2x^2 + 9x - 18