You have to use these facts:
1) The derivative of a sum is the sum of the derivatives
2) d[x^n] / dx = n x ^ (n - 1)
3) d [a(f(x) ] / dx = a d [f(x)] / dx
=> d [x^3 + 3x^2 + 5] / dx = d[x^3]/dx + 3d[x^2]/dx + 0
= 3x^2 + 6x
Answer: option D. 3x^2 + 6x