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

1. The question asks to identify which of the listed substances, when in excess in the environment, cause acid rain. 2. Acid rain is primarily caused by emissions of Sulphur dioxide (SO2) and Nitrogen oxides (NOx) reacting with water, oxygen, and other chemicals in the atmosphere to form sulfuric and nitric acids. 3. Nitrogen oxide (item 2) is a known precursor to acid rain. 4. Sulphur dioxide (item 4) is another major precursor to acid rain. 5. Carbon monoxide (item 1) is a pollutant but does not significantly contribute to acid rain formation. 6. Ozone (item 3), particularly ground-level ozone, is a component of smog and a harmful pollutant, but it is not considered a direct cause of acid rain. 7. Therefore, excess Nitrogen oxide and Sulphur dioxide are causes of acid rain.