Carbon monoxide is basically formed when an object is burned. Methane, which is a natural gas produces  CO after oxidation. Methane, produces less CO as compared to other units of gas. Incomplete combusion results in creation of poisonous CO. It occurs when supply of oxygen is poor. 

Governments have already taken action against air pollution by introducing green energy. Like wind energy, solar energy and renewable energy to minimize burning of  fuels which cause heavy air pollutions.

The concept of 'Reduce, reuse and recycle helps us to minimize the dependence on producing new things. 

Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline, petrol, biodiesel blends, diesel fuels, fuel oils, or coal. The largest part of most combustion gas is nitrogen. water vapour (except with pure-carbon fuels), and carbon dioxide (except for fuels without carbon); these are not toxic or noxious. A relatively small part of combustion gas is undesirable noxious or toxic substances, such as carbon monoxide (CO) from incomplete combustion.

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere. The exchange of incoming and outgoing radiation that warms the Earth is often referred to as the greenhouse effect because a greenhouse works in much the same way. Incoming UV radiation easily passes through the glass walls of a greenhouse and is absorbed by the plants and hard surfaces inside. Weaker IR radiation, however, has difficulty passing through the glass walls and is trapped inside, thus warming the greenhouse. This effect lets tropical plants thrive inside a greenhouse, even during a cold winter.

Carbon monoxide is an air pollutant. It is found in cigarette smoke and emissions from motor vehicles, industrial processes, and poorly ventilated combustion sources.

In adsorption method,the polluted air is passed through porous solid adsorbents kept in suitable containers. The gaseous pollutants are adsorbed at the surface of the porous solid and clean air passes through.

In absorption method,the polluted air containing gaseous pollutants is passed through a scrubber containing a suitable liquid absorbent. The liquid absorbs the harmful gaseous pollutants present in air.

The ozone hole is caused by the effect of pollutants in the atmosphere destroying stratospheric ozone. During the Antarctic winter something special happens to the Antarctic weather.

Firstly, strong circular winds form that blow around the whole continent, this is known as the "polar vortex" -  this isolates the air over Antarctica from the rest of the world.

Secondly, special clouds form called Polar Stratospheric Clouds. Clouds don't normally form in the stratosphere and these turn out to have the effect of concentrating the pollutants that break down the ozone, so speeding the process up.

Photochemical smog is produced when pollutants from the combustion of fossil fuels react with sunlight. The energy in the sunlight converts the pollutants into other toxic chemicals. For photochemical smog to form, there must be other pollutants in the air, specifically nitrous oxides and other volatile organic compounds (VOCs).

Hence, the correct option is $A$

Plants play a very important part in reducing the amount of $CO _2$ in atmosphere, plants use $CO _2$ to make food and release oxygen, during rain, water get reacted with $CO _2$ in the atmosphere and form $H _2CO _3$ and hence reduce the amount of $CO _2$ in the atmosphere.

The incomplete combustion of petrol and diesel in automobile produces carbon monoxide.

In large cities, environmental health can be maintained by decreased use of insecticides as it affects air quality. All types of household and industrial waste should be handled and disposed of out of the city area and factories inside the residential areas cause great harm to health by polluting the air and water by its wastes, so they must be shifted outside the residential area.

We can save the environment from degradation by reducing the amount of fossil fuels to be burned:

As with many direct and indirect greenhouse gases, reductions in carbon monoxide emissions can most effectively be made through direct reductions in fossil fuel use. There is some evidence that the widespread use of catalytic convertors in cars has significantly reduced carbon monoxide emissions from this source. 

The Mathura Refinery, owned by Indian Oil Corporation, is located in Mathura, Uttar Pradesh. The Mathura oil refinery releases toxic gases and disposes waste into the rivers making the area dirty and unhealthy. Even the Taj Mahal is getting affected because of this. The India government hired a panel to examine the effects of the refinery on the Taj Mahal. The panel found that the air has high levels of suspended particulate matter, caused by factory emissions, dust, construction, and exhaust from automobiles. These are causing the Taj Mahal to change colour.

Aerosols are minute particles suspended in the atmosphere. When these particles are sufficiently large, we notice their presence as they scatter and absorb sunlight. Their scattering of sunlight can reduce visibility (haze) and redden sunrises and sunsets. Aerosols also can act as sites for chemical reactions to take place. The most significant of these reactions are those that lead to the destruction of stratospheric ozone. During winter in the Polar Regions, aerosols grow to form polar stratospheric clouds. The large surface areas of these cloud particles provide sites for chemical reactions to take place. These reactions lead to the formation of large amounts of reactive chlorine and, ultimately, to the destruction of ozone in the stratosphere

Aerosols are emitted into the air in the form of vapour or fine mist. Jet airplanes emit aerosols containing chlorofluorocarbons $(CCl _{2}F _2)$ and $(CCl _3F)$. The aerosols deplete ozone layer in the atmosphere.

Air pollution could be both due to natural or man-made causes. The major factors affecting composition of air are: area of forests in the region (potential cause of forest fires), industries present in the area, density of population, urbanization, etc.

The day to day condition of the atmosphere at a place with respect to $temperature, humidity, rainfall\, and\, wind-speed$ are called the weather at that place.

Carbon dioxide is the major gas along with smaller amounts of methane and nitrous oxide which are emitted by the combustion of fossil fuels such as coal, oil, and natural gas and contribute to the major green house gases.

Effects of Air Pollution are greenhouse effect, smog, deforestation and acid rains.

Causes of Air pollution are

Air pollution takes place in two different layers of the earth's atmosphere : troposphere and stratosphere.

Carbon Monoxide is formed by improper or incomplete combustion and is generally emitted from vehicles. 

$SO _2, \ NO _2 $ & $ CFC $, all cause air pollution.

Carbon monoxide reduces the oxygen-carrying capacity of the blood.

Soot, Smog, CFCs are all air pollutants.

Option A is the correct answer.

Thermal pollution is when an industry or other human-made organization takes in water from a natural source and either cools it down or heats it up. They then eject the water back into the natural resource, which changes the oxygen level and can have a disastrous effect on the local ecosystem. 

Environmental pollution can be controlled by treating factory wastes before disposing of them. So, if we treat wastewater before disposing of in a river, it will surely decrease the amount of dumped pollutants.