What is the completely factored form of 3x^5 – 7x^4 + 6x^2 – 14x?

A. (x^4+2x)(3x-7)

B. x^4(3x-7)(2x-1)

C. x(x^3+2)(3x-7)

D. x(3x^4-7x^3+6x-14)