Correct Answer :- a

Explanation : Classical smog does not contain any secondary pollutants. It is a mixture of fog, sulfur dioxide and coal smoke particulates

Photochemical smog is composed of primary and secondary pollutants.Primary pollutants, which include nitrogen oxides and volatile organic compounds, are introduced into the atmosphere via vehicular emissions and industrial processes.Secondary pollutants, like ozone, result from the reaction of primary pollutants with ultraviolet light. It is most common in sunny and dry cities, like Los Angeles.

Carbon dioxide is a quantitative pollutant. This gas is already present in environment in small quantity. When its concentration increases in the environmentit is termed as pollutant. It may cause greenhouse effect also.

Electrostatic precipitator is used to remove particulate matters from chimneys of factories. The dust collection efficiency of electrostatic precipitator is affected by the particle siz of the aerosol to be collected so, the collection efficiency is high for large particles and low for the small particles.

Planting trees on both the side of roads and highways is called providing green muffler. It is done to reduce noise pollution to nearby residential areas.

Irreparable computers and other electronic goods are known as e-wastes or electronic wastes. E-wastes are buried in landfills or incinerated.

For removing particulate pollutants from air various methods are applied such as use of activated charcoal and calcium hydroxide that absorbs the particulate matters form polluted air.

Deoxygenation of water bodies means reducing the oxygen from the water. Deoxygenation do not convert eutrophic water body back into oligotrophic. In such waters growth of anaerobic microbes producing secondary pollutants like H₂ S.so, the statement i is wrong and ii  is correct.

Huge quantity of sewage is dumped in a river, the BOD will increase as sewage contain large amount of organic matter that support large number of aquatic microbes that consume oxygen present in water.

Acid rain is due to air pollution. Burning of fossils fuels release sulphur dioxide and nitrogen oxides that combine with water to form sulphuric acid and nitric acid during rain.

Eutrophication of water body occurs due to addition of detergents, fertilizers and untreated sewage.