Which one of the following is the main reason of acid rains ?

Acid rain is primarily caused by the presence of sulfur dioxide (SO2) and nitrogen oxides (NOx) in the atmosphere [2]. These gases are released into the air through natural sources like volcanoes and anthropogenic activities, most notably the burning of fossil fuels in power plants and motor vehicle exhausts [3]. Once in the atmosphere, these oxides undergo chemical reactions with water, oxygen, and other oxidants to form sulfuric acid (H2SO4) and nitric acid (HNO3) [4]. The dissolution of these acidic compounds into rainwater significantly lowers its pH, typically to values between 4.2 and 4.4, compared to the normal rain pH of 5.6 [4]. While minerals and dust particles may interact with rain, they are not the primary drivers of acidification; rather, the dissolution of sulfur and nitrogen oxides is the fundamental mechanism behind the formation of acid precipitation [1].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 6: Geomorphic Movements > Anthropogenic Solution Weathering > p. 90
2. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Acidification > p. 8
3. [3] https://www.usgs.gov/water-science-school/science/acid-rain-and-water
4. [4] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 5: Environmental Pollution > 5.I5. ACID RAIN > p. 101