Answer the following.
Which are invisible pollutions?

Hint:Air pollution is the spread of the contaminants in the air. These are classified into many types out of which the visible and the invisible pollutants are also the one. They are released by the process of burning, from industries or factories, etc.

Complete step by step solution:
The visible pollutants are visible to the naked eye. It includes smog, nitrogen oxides, Sulphur dioxide, volatile organic compounds, ozone and the aerosols. The smog is made from the smoke, fog and the other suspended particles. The vehicle like cars, trucks and others releases the nitrogen dioxide which is the brown gas. The aerosols is the white gas released from cars, power plants etc. The invisible pollutants are not visible to the naked eye, they are emitted in the outer atmosphere and their presence is known only if some amount of air is tested. The example of this pollutant is carbon monoxide, methane etc. The carbon monoxide is colorless gas that is released into the atmosphere when the coal, oil and the gas are burned. Methane is the flammable gas and it is the greenhouse gas causing global warming. But these are present in very small quantities in the atmosphere.

Note:These pollutants may cause severe health effects in the human, animals, plants and the other organisms. The air pollutants like nitrogen oxides, Sulphur oxides, carbon monoxides can cause more disturbances to the working of the lungs by causing the obstruction in airways, restricting expansion of the lungs.