Which type of pollution is caused by the spraying of $DDT$ on crops?

Which of the following is the most significant air pollutant in modern times?

The main pollutant from automobile exhaust is

Some reactions of $NO_2$ relevant to photochemical smog formation are:
$NO_{2(g)} \xrightarrow{hv} NO_{(g)} + X$
$X + O_2 \rightarrow Y$
$NO + Y \rightarrow NO_2 + A$
$O + O_2 + M \rightarrow B + M$
Identify $A, B, X$ and $Y$.

The living organisms on or around the earth constitute

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