Option 1: Long winter nights

Long winter nights alone do not contribute significantly to the formulation of smog. While the increased duration of nighttime may allow for the accumulation of pollutants, it is not the most important factor in smog formation.

Option 2: Formation of an ‘inversion lid’

The formation of an "inversion lid" is a crucial factor in smog formation. An inversion lid occurs when a layer of warm air traps cooler air and pollutants close to the surface. This prevents the dispersal of pollutants and leads to the build-up of smog.

Option 3: Presence of many air pollutant resources

This option is correct. The presence of multiple air pollutant resources, such as industrial emissions, vehicle emissions, and burning of fossil fuels, is a significant factor in smog formation. These pollutants react with sunlight and other chemicals in the atmosphere to form smog.

Option 4: Rapid fall in temperature with increasing height above the sea level

While temperature changes can affect the behavior of air pollutants, a rapid fall in temperature with increasing height above sea level is not the most important factor for smog formation.

In conclusion, the correct answer is option 3 - the presence of many air pollutant resources is the most important factor for