Water samples with $BOD$ values of $4 \ ppm$ and $18 \ ppm$ respectively are:

$A$ water sample has $ppm$ level concentration of following anions:
$F^- = 10; \, SO_4^{2-} = 100; \, NO_3^- = 50$
The anion/anions that make/makes the water sample unsuitable for drinking is/are:

From where are the biodegradable wastes generated?

Which among the following statements is $NOT$ true according to principles of green chemistry?

Match the following:
| List-$I$ | List-$II$ |
| :--- | :--- |
| $A$. Methemoglobinemia | $I$. $1 \ ppm$ of dissolved oxygen in water |
| $B$. Kidney damage | $II$. $1000 \ ppb$ of lead in drinking water |
| $C$. Bones and teeth damage | $III$. $BOD$ of drinking water is $2 \ ppm$ |
| $D$. Growth of fish is stopped | $IV$. $2000 \ ppm$ of nitrates in drinking water |
| | $V$. $50 \ ppm$ of fluoride in drinking water |

Give the details of the different layers of the atmosphere and briefly describe the substances present in them.