Which factor is most likely to affect the severity of smog in urban areas?

The severity of smog in urban areas is most closely linked to levels of traffic and industrial activity. This is due to the release of pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) from vehicles and industries, which are significant contributors to the formation of smog, particularly photochemical smog.

In urban environments, heavy traffic generates large amounts of exhaust emissions that combine with sunlight to create ground-level ozone, a primary component of smog. Additionally, industrial activities often emit similar pollutants, adding to the smog formation potential. Regions with high traffic and industrial outputs are therefore more susceptible to reduced air quality and increased smog severity, particularly on hot, sunny days when ozone formation is magnified.

Other factors, like the age of buildings, the effectiveness of public transportation, and the geographical location of a city, while they can influence overall urban living conditions and air quality, do not have as direct an impact on smog severity as traffic and industrial emissions. For example, older buildings may not necessarily contribute significantly to smog, and while a good public transportation system might reduce traffic levels, it isn't a direct cause of smog itself. Similarly, geographical location can affect air quality but is not a primary factor