Factor he expression

-216x^3+1

A. (-6x+1)(36x^2+6x+1)

B. (-6x+1)^3

C. (-6x-1)(36x^2-6x+1)

D. prime polynomial

I know the problem is not a prime polynomial. I came up with -(6x-1)(36x^2+6x+1). This answer is not listed, What did I do wrong.