Which expressions are completely factored?

Select each correct answer.

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

18x^4−12x^2=6x(3x^3−2x)

20x^3+12x^2=4x^2(5x+3)

24x^6−18x^5=6x^5(4x−3)