$A$ water sample is considered the cleanest based on which of the following $BOD$ values (in $ppm$)?

Which of the following diseases increases in prevalence due to the greenhouse effect?

Observe the following statements:
Statement-$I$: The carbon-containing components of photochemical smog are acrolein,methanal,and $PAN$.
Statement-$II$: The number of greenhouse gases in the list given below is $5$: $CH_4, CO_2, NO, H_2O_{(l)}, H_2O_{(g)}, O_2, O_3$.
The correct answer 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

Mention the harmful effect of ultra violet radiations.

Which of the following methods can be used to control water pollution?