Pure water would have a $BOD$ value of

Which of the following is a lung irritant?

Arrange the following hydrocarbon fuels in increasing order of their polluting strength: $LPG$,$CNG$,and Kerosene.

The term biosphere is used for the zone of the earth where life exists:

On the surface of polar stratospheric clouds,hydrolysis of chlorine nitrate $(ClONO_2)$ gives $A$ and $B$,while its reaction with $HCl$ produces $B$ and $C$. $A, B$ and $C$ are,respectively:

The acceptable level of carbon monoxide gas $(CO)$ in the atmosphere in $ppm$ level is