Fill in the blanks:
$(1)$ $.......$ is made using fly ash and slag from the steel industry.
$(2)$ Biogas is used in the production of $.......$ and its byproduct is used as $.......$.

$A$ factory was started near a village. Soon,the villagers began experiencing the presence of undesirable gases in the atmosphere,leading to symptoms like headaches,chest pain,colds,dry throats,and breathing difficulties. The villagers blamed the smoke emitted from the factory chimney for these problems. Describe what might have happened and provide the chemical equations to support your explanation.

The living organisms or the surroundings of the earth's composition are known as .....

The $F^{-}$ ions make the enamel on teeth much harder by converting hydroxyapatite (the enamel on the surface of teeth) into much harder fluoroapatite having the formula.

Which of the following is a lung irritant that can lead to an acute respiratory disease in children?

What are the major pollutants in large cities?