Increased ozone in the lower atmosphere (near the ground) primarily results from automobile exhaust. Option B.
Ozone layer in the lower atmosphere
Ground-level ozone is a major component of smog and is primarily formed by the reaction of nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight.
Automobile exhaust is a significant source of both NOx and VOCs, contributing to the formation of ground-level ozone.
Option A (CFC pollution) is not a major contributor to ground-level ozone. Options C (carbon dioxide production) and D (all of the above) are not directly related to the formation of ground-level ozone.