Photo-chemical smog is a problem in

The correct answer is C. Areas with a lot of sunlight and high vehicle use.

Photo-chemical smog is formed when sunlight reacts with pollutants like nitrogen oxides and volatile organic compounds, which often come from vehicle emissions. This type of smog is most prevalent in urban areas with high traffic and plenty of sunlight, contributing to air quality issues. If you have further questions or need more detailed explanations, feel free to ask!