The average rate of change of a function over a interval [a,b] is given by:
[tex]r=\frac{f(b)-f(a)}{b-a}[/tex]
Where, in this case:
[tex]\begin{gathered} a=1 \\ b=2 \\ f(a)=0 \\ f(b)=3 \\ so: \\ r=\frac{3-0}{2-1}=\frac{3}{1}=3 \end{gathered}[/tex]
Answer:
D. 3
