Answer
$(C)$
Work Step by Step
Calculate the average rate of change over the intervals $[1,8],[2,8],...,[7,8]$
$\left[\begin{array}{ccc}
a & b & [f(b)-f(a)]/(b-a)\\ \hline
1 & 8 & -0.1/7\\
2 & 8 & -0.2/6\\
3 & 8 & -0.3/5\\
4 & 8 & -0.3/4\\
5 & 8 & -0.3/3\\
6 & 8 & -0.2/2\\
7 & 8 & -0.1/1
\end{array}\right] $
Not one is positive.
Thus, the answer is $(C)$
