Air Pollution

High concentration of CO₂ in atmosphere has been the main component of greenhouse effect.

Sulphur dioxide causes acid rain.

Nitrogen oxides (NO_X), especially nitrogen dioxide, are emitted from high temperature combustion and can be seen as the brown haze dome above or plume downwind of cities.

Coal-fired power plants are the largest source of mercury pollution as mercury exists naturally in coal. Cement kilns are used for the manufacture of hydraulic cement and coal, which is a major source of mercury, is used to fuel the cement-manufacturing process. Incinerator is waste treatment process that involves the combustion of organic substances contained in waste materials. Supersonic jets release nitrogen oxide, and not mercury.

CNG is a cleaner fuel. It is being promoted in cities with high air pollution. CNG combustion produces fewer undesirable gases than the other fuels. It is safer than other fuels in the event of a spill because natural gas is lighter than air and disperses quickly when released. 

Lead and other heavy toxic metals or aerosols (solid or liquid gases which can spread through the air and are transported by) out of a fireplace like black or brown uncultivable smoke and fly ash in the air (contaminated soil and waste) pollute the air of a busy city.

Correct Answer: Carbon monoxide

Yes, it is the correct answer. Sulphur dioxide, when produced in excess, rises high in the atmosphere and reacts with water to produce sulphuric acid. This causes acid rain.

Free oxygen will not cause any atmospheric pollution.

The fog deposited with smoke and chemical fumes forms a dark and thick covering called smog.

Automobiles run by petrol and diesel produce carbon monoxide, which is a dangerous pollutant of air.

Acid rain is primarily caused by nitrogen dioxide (NO2) and sulphur dioxide (SO2) emitted from fossil fuel combustion and industrial processes. These gases react with atmospheric water to form nitric and sulphuric acids.

Sulfur dioxide is a key contributor to industrial smog, formed when sulfur-containing fuels are burned. Areas with high concentrations of industrial activity and coal combustion typically experience elevated sulfur dioxide levels, which react with moisture and other pollutants to form smog.