The Following Table Shows the Number of Bird Species Found $A$

Multiple Choice

The following table shows the number of bird species found on an island of area $A$ square miles that is part of a particular Pacific island chain. $$\begin{array} { | l | l | l | l | l | l | } \hline A = \text { area } & 10 & 20 & 30 & 40 & 50 \\\hline \begin{array} { l } W = \text { number } \\\text { of species }\end{array} & 25 & 31 & 36 & 39 & 42 \\\hline\end{array}$$ Calculate the average rate of change in the number of species as the area changes from 30 to 40 square miles.

A) 1.52 species per square mile
B) 39 species per square mile
C) 0.3 species per square mile
D) None of the above