Acid rain is primarily caused by the excess presence of nitrogen oxide and sulphur dioxide in the environment. * Carbon monoxide is not a direct cause of acid rain. It is a pollutant that contributes to the formation of ground-level ozone, but it does not lead to the production of acid rain. * Nitrogen oxides, which include nitric oxide and nitrogen dioxide, are major contributors to acid rain. When these gases react with water, oxygen, and other substances in the atmosphere, they form nitric acid, a key component of acid rain. * Ozone is not a direct cause of acid rain. While ozone can have negative environmental impacts, it is not a precursor to the formation of acid rain. * Sulphur dioxide is another primary contributor to acid rain. When Sulphur dioxide combines with water, oxygen, and other substances in the atmosphere, it forms sulphuric acid, which is also a major component of acid rain.