What are the possible rational zeros of f(x) = x^4 + 6x^3 − 3x^2 + 17x − 15?

± 1, ± 3, ± 5, ± 15
± 1, ± 1/3, ± 1/5, ± 1/15
± 1, ± 3, ± 6, ± 15, ± 17
± 1, ± 1/3, ± 1/6, ± 1/15, ± 1/17