Excess of which of the above in the environment is/are cause(s) of acid rain? 1. Carbon monoxide 2. Nitrogen oxide 3. Ozone 4. Sulphur dioxide

Acid rain is primarily caused by the emission of sulfur dioxide (SO2) and nitrogen oxides (NOx) into the atmosphere. These gases react with water, oxygen, and other chemicals to form sulfuric acid and nitric acid, which then fall to the Earth as acid rain (wet deposition) or dry particles and gases (dry deposition).

1. Carbon monoxide: Carbon monoxide (CO) is a poisonous gas formed from incomplete combustion. It is a major air pollutant but does not directly cause acid rain.
2. Nitrogen oxide: Nitrogen oxides (NOx), particularly NO2, are significant precursors to acid rain. They are primarily released from the combustion of fossil fuels in vehicles and power plants.
3. Ozone: Ozone (O3) is a powerful oxidant and a component of photochemical smog, but it is not a direct cause of acid rain in terms of forming the acidic components.
4. Sulphur dioxide: Sulfur dioxide (SO2) is a major contributor to acid rain, mainly from the burning of fossil fuels (especially coal) in power plants and industrial facilities. Therefore, nitrogen oxide and sulfur dioxide are the primary causes of acid rain among the given options.