The correct answer is option 3: Sulphur dioxide.

Acid rain is caused by the emission of certain pollutants into the atmosphere. These pollutants react with water vapor in the air to form acidic compounds, which then fall back to the Earth`s surface in the form of rain, snow, or other precipitation.

Option 1, Ozone, is not a cause of acid rain. Ozone is a beneficial gas that occurs naturally in the Earth`s atmosphere. It forms a protective layer, known as the ozone layer, which shields the Earth from harmful ultraviolet radiation from the sun.

Option 2, Ammonia, is also not a cause of acid rain. Ammonia is a compound consisting of nitrogen and hydrogen, and it is commonly used in fertilizers. Although ammonia does contribute to air pollution, it does not directly lead to the formation of acid rain.

Option 4, Carbon monoxide, is also not a cause of acid rain. Carbon monoxide is an odorless and colorless gas that is produced from the incomplete combustion of fossil fuels. It is primarily known for its toxic effects on human health, but it does not play a role in the formation of acid rain.

Therefore, the correct cause of acid rain is option 3: