Let $\mathbb{R}$ be the set of all real numbers. The function $f : \mathbb{R} \rightarrow \mathbb{R}$ defined by $f(x) = x^3 - 3x^2 + 6x - 5$ is\\
(A) one-to-one, but not onto\\
(B) one-to-one and onto\\
(C) onto, but not one-to-one\\
(D) neither one-to-one nor onto