Example of primary pollutant:
This question has multiple correct options
$A.\;S{O_2}$
$B.\;C{O_2}$
$C.\;Hydrocarbon$
$D.\;CO$

Hint: For answering these types of questions we must understand the meaning of primary pollutant and the materials from which these pollutants come.

Complete answer:
Pollutants emitted directly from identifiable sources or are in their unmodified forms and pose health risks are known as primary pollutants. These are emitted from cars, coal-fired power plants, natural gas power plants, biomass burning, natural forest fires, volcanoes, etc.
When primary pollutants interact with one another or sunlight or natural gases they produce new and harmful compounds known as secondary air pollutants.
Some of the major materials released directly into the atmosphere in unmodified forms are as follows:
Carbon monoxide, sulfur dioxide, nitrogen oxides, hydrocarbons, particulate matter and carbon Monoxide
Primary pollutants are produced by burning of organic material like coal, gas, wood, trash, etc. They are toxic because they bind with hemoglobin and reduce oxygen in blood.
> Sulphur dioxide ($S{O_2}$) is produced due to human activities such as the burning of coal or oil and due to natural sources, such as volcanoes. It becomes very dangerous when it transforms into sulfuric acid (${H_2}S{O_4}$), which is also known as acid rain.
> Carbon dioxide ($C{O_2}$) is mainly produced when living organisms breathe, but this gas is majorly produced by cars, planes, power plants, and other human activities that involve the burning of fossil fuels such as gasoline and natural gas.
> Hydrocarbons are organic compounds which consist of hydrogen and carbon. They are produced by incomplete burning or evaporation from fuel supplies where automobiles are a major contributor but they are also produced by industries.
> Carbon monoxide ($CO$) is produced due to incomplete combustion of organic matter. It is mainly contributed by vehicles in traffic. This gas is flammable and toxic to people even in small concentrations. It is associated with $C{O_2}$ and ozone.

Hence our answer is option A and option D. i.e. $S{O_2}$ and $CO$ are primary pollutants.

Note: Primary Pollutants are the ones which are injected into the atmosphere directly. Examples of primary pollutant are carbon monoxide ($CO$), oxides of nitrogen ($N{O_x}$​, $NO$), sulfur oxides ($S{O_x}$​), volatile organic compounds (VOCs), particulate matter such as dust, ash, salt particles etc.