AHSME 1962 Problem 9

When $x^9-x$ is factored as completely as possible into polynomials and monomials with integral coefficients, the number of factors is: $\textbf{(A)}\ \text{more than 5} \textbf{(B)}\ 5 \textbf{(C)}\ 4 \textbf{(D)}\ 3 \textbf{(E)}\ 2$