John's Total Private Benefit Exceeds His Total Private Cost by the Greatest

John's total private benefit exceeds his total private cost by the greatest amount when he carries out 10 units of an activity. Also, at 10 units, the marginal social benefit from John's activity exceeds its marginal social cost by the greatest amount. Based on this information, society's net benefit from John's activity:

A) is maximized when he carries out 10 units.
B) would increase if he carried out less than 10 units.
C) would increase if he carried out more than 10 units.
D) always moves in the same direction as John's net benefit from the activity.