Can someone please explain to me how to solve this?

For x≥0, [tex]\sqrt{x^5}[/tex] + [tex]\sqrt{9x}[/tex] =

(A) (x²+ 3)√x

(B) 10[tex]\sqrt{x^6}[/tex]

(C) [tex]\sqrt{x^5+9x}[/tex]

(D) x²+ 3

(E) 3x²