The Following Data Show the Relationship Between the Number of Drivers

The following data show the relationship between the number of drivers who leave for work at 8:00 a.m., their average commute time, and their marginal benefit of commuting. $$\begin{array} { | c | c | c | } \hline \begin{array} { c } \text { Number of Drivers } \\\text { Who Leave at } 8 \text { am }\end{array} & \begin{array} { c } \text { Average } \\\text { Commute Time }\end{array} & \begin{array} { c } \text { Marginal } \\\text { Benefit }\end{array} \\\hline 100 & 30 \text { minutes } & \$ 10 \\\hline 200 & 65 \text { minutes } & \$ 8 \\\hline 300 & 110 \text { minutes } & \$ 4 \\\hline 400 & 170 \text { minutes } & \$ 3 \\\hline 500 & 260 \text { minutes } & \$ 1 \\\hline\end{array}$$ If there is no charge to use the highway, then one would expect that ______ the socially optimal number of drivers will leave at 8:00 a.m. because ______.

A) more; each driver's use of the highway imposes an external cost on other drivers by increasing the commute time
B) more; the social marginal benefit of using the highway is greater than the private marginal benefit
C) less; each driver's use of the highway imposes an external cost on other drivers by increasing the commute time
D) less; the private marginal benefit of using the highway is greater than the social marginal benefit