Here we have to choose the way which is not the common way to judge the quality of the air in a particular area.
The measuring the amount of precipitation in the area is not the common way to determine air quality in an area.
The acidity of the rain causes due to the excess amount of CO₂ and SO₂ in an area. Both the gases cause pollution.
The measuring of the amount of a particular gas element is a renowned way to determine the pollution level of an area.
The ozone is a harmful gas so the measuring of its amount in ground level can identify the level of pollution in the particular area.