Air Pollution

Smog is a type of air pollutant, is a combination of smoke and fog. Classic smog results from large amounts of coal burning in an area and its caused by a mixture of smoke and sulphur dioxide.

Smog is often caused by heavy traffic, high temperatures, sunshine and calm winds.

Air pollution from burning of fossil fuels is the major cause of acid rain. The main chemicals in air pollution that create acid rain are sulfur dioxide ($SO _2$) and nitrogen oxides. Acid rain usually forms high in the clouds where sulfur dioxide and nitrogen oxides react with water, oxygen, and oxidants. this mixture forms a mild solution of sulfuric acid and nitric acid. Sunlight increases the rate of most of these reactions. Rainwater, snow, fog, and other forms of precipitation containing those mild solutions of sulfuric and nitric acids fall to earth as acid rain.

The main chemicals in air pollution that create acid rain are $SO _2$ and $NO _x$. 

Industries like Mathura Oil refinery near Agra emits certain suspended particulate matter like soot particles. This results in yellowing of marble of the monument.

At ground level, ozone is an air pollutant that is a major component of smog which is dangerous for both humans and plants. Long-term ozone exposure has also been shown to reduce life expectancy. 

Acid rain is a rain or any other form of precipitation that is unusually acidic, meaning that it possesses elevated levels of hydrogen ions (low pH). It can have harmful effects on plants, aquatic animals and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids. 

The major natural causal agent for acid rain is volcanic emissions. Volcanoes emit acid producing gases to create higher than normal amounts of acid rain or any other form of precipitation such as fog and snow to an extent of affecting vegetation cover and health of residents within the surrounding. 

The principal cause of acid rain is sulfur and nitrogen compounds from human sources, such as electricity generation, factories, and motor vehicles. Electrical power generation using coal is among the greatest contributors to gaseous pollutions that are responsible for acidic rain. The gases can be carried hundreds of kilometers in the atmosphere before they are converted to acids and deposited.

Photochemical smog is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone.
Hence option A is the correct answer.

Smog is two types:-
1) Classical smog is also called as London smog or sulphurous acid smog.
2) Photochemical smog is also called as Los angles smog.

Smog is two types:
1) Classical smog is also called as London smog or sulphurous acid smog.
2) Photo chemical smog is also called as Los angles smog.

Smog is two types:
1) Classical smog is also called as London smog or sulphurous acid smog.
2) Photochemical smog is also called as Los angles smog. 
Hence option D is correct.

$SO _2$ is a major gaseous pollutant found in the lower atmosphere. They are the compounds of sulphur and oxygen molecules. So when the fuels such as coal and oil are burnt, it leads to emission of $SO _2$ gas.