Why does acid rain occur? 

All of these 

The correct answer is option 4. All of these.

Sulfur dioxide and nitrogen oxides are released into the atmosphere through microbiological activities, earthquakes, natural fires, lightning, and volcanic eruptions. However, the majority of sulphur dioxide emissions are brought on by human activity owing to the burning of fuel in industries and power plants, and half of nitrogen oxide emissions are brought on by gases created by automobiles. Similar to this, although to a lesser level, ammonia is produced by intensive animal rearing due to the breakdown of organic materials.

These three pollutants, which are capable of traveling great distances from their point of origin, oxidize when they come into contact with the atmosphere, producing sulphuric acid and nitric acid. These acids, which can also appear as snow or fog, dissolve in water droplets in the clouds and fall to the earth's surface as acid rain.