Which of the following functions best describes this graph?

Answer D is correct.  The two factors (x - 6) and (x - 3) become zero at x = 6 and x = 3, respectively, showing the x-intercepts of this graph.  Additionally, we can see that the sign of the leading coefficient of f(x) = (x - 6)(x - 3) is +, which indicates that the curve opens up.  This agrees with the given graph.

Step-by-step explanation:

The two factors (x - 6) and (x - 3) become zero at x = 6 and x = 3, respectively, showing the x-intercepts of this graph.  Additionally, we can see that the sign of the leading coefficient of f(x) = (x - 6)(x - 3) is +, which indicates that the curve opens up.  This agrees with the given graph.  Answer D is correct.

this may not be at all, but i use the same website you're using for school, and if i'm stuck doing one of these i try to look for it on the section.