Answer
$(B)$
Work Step by Step
Calculate the average rate of change over the intervals $[2,6],[3,6],[4,6],$ and $[5,6] .$
$\left[\begin{array}{cccl}
a & b & [f(b)-f(a)]/(b-a) & \\
& & & \\
2 & 6 & 0.15/4 & =+0.375\\
3 & 6 & 0/3 & =0\\
4 & 6 & -0.05/2 & =-0.025\\
5 & 6 & -0.10 /1 & =-0.100
\end{array}\right] $
We see a decrease, year by year.
Thus, the answer is $(B)$
