Which is the greatest source of air pollution these days?

Methane gas has a global warming potential approximately $25$ times that of which of the following gases?

Sewage containing organic waste should not be disposed of in water bodies because it causes major water pollution. Fishes in such polluted water die because of:

Which of the following practices will not come under green chemistry?

Statues and monuments in India are affected by acid rain. How?

Fill in the blanks:
$(1)$ $A$ special cloud is formed over the Antarctica region in winter,which is called ..............
$(2)$ $A$ known source of pollution is called ..............
$(3)$ An unknown source of pollution is called ..............
$(4)$ The concentration of dissolved oxygen in water is ......... and the concentration of dissolved oxygen in air is ............