Which expressions are completely factored?

Select each correct answer.

A.20x3+12x2=4x2(5x+3)

B.18x^4−12x^2=6x(3x^3−2x)

C.12x^5+8x^3=2x^3(6x^2+4)

D.24x^6−18x^5=6x^5(4x−3)