Biochemical Oxygen Demand,$(BOD)$ is a measure of organic material present in water. $BOD$ value less than $5 \ ppm$ indicates a water sample to be ..... .

From the following,identify the reactions which are responsible for the depletion of the ozone layer.
$I. Cl\dot{O}_{(g)} + NO_{2_{(g)}} \rightarrow ClONO_{2_{(g)}}$
$II. CF_2Cl_{2_{(g)}} \xrightarrow{uv} \dot{Cl}_{(g)} + \dot{CF}_2Cl_{(g)}$
$III. \dot{Cl}_{(g)} + CH_{4_{(g)}} \rightarrow HCl_{(g)} + \dot{C}H_{3_{(g)}}$
$IV. \dot{Cl}_{(g)} + O_{3_{(g)}} \rightarrow Cl\dot{O}_{(g)} + O_{2_{(g)}}$
$V. Cl\dot{O}_{(g)} + O_{(g)} \rightarrow \dot{Cl}_{(g)} + O_{2_{(g)}}$

Why is it safer to use soap from the environmental point of view?

State whether the following statements are true or false:
$(1)$ Mist is produced by particles of spread liquid and by condensation of vapour in air.
$(2)$ Particulate matter of size up to $5 \ \mu m$ reaches directly into the lungs.
$(3)$ Ozone and nitric oxide cause irritation in the nose and throat.

Water pollution is caused due to

Global warming is due to an increase of: