Dinitrogen is a robust compound,but reacts at high altitude to form oxides. The oxide of nitrogen that can damage plant leaves and retard photosynthesis is

Two statements are given below.
Statement-$I$: In dry cleaning,the solvent $Cl_2C=CCl_2$ was earlier used and now it is replaced by liquified $CO_2$.
Statement-$II$: In bleaching of paper,$H_2O_2$ was used earlier and now it is replaced by chlorine gas.
Correct answer is

Sulphur dioxide is one of the components of polluted air. $SO_{2}$ is also a major contributor to acid rain. The correct and complete reaction to represent acid rain caused by $SO_{2}$ is ..... .

The common components of photochemical smog are

When a huge amount of sewage is dumped into a river,the $BOD$ will

Which is the greatest source of air pollution these days?