Answer:
The correct option is C.
Step-by-step explanation:
The width of the rectangular pen is
[tex]w=x^3-2x+3x^2+15[/tex]
The length of the rectangular pen is
[tex]l=x^4-x^2+11x^3-5[/tex]
The perimeter of a rectangle is
[tex]P=2(l+w)[/tex]
[tex]P=2(x^4-x^2+11x^3-5+x^3-2x+3x^2+15)[/tex]
[tex]P=2(x^4+12x^3+2x^2-2x+10)[/tex]
[tex]P=2x^4+24x^3+4x^2-4x+20[/tex]
Therefore the correct option is C.