Air pollution that occurs in sunlight is

Which of the following is least biodegradable?

Which of the following statement$(s)$ is (are) incorrect reason for eutrophication?
$A$. excess usage of fertilisers
$B$. excess usage of detergents
$C$. dense plant population in water bodies
$D$. lack of nutrients in water bodies that prevent plant growth
Choose the most appropriate answer from the options given below:

Explain why sometimes foaming is seen in river water near the place where sewage water is poured after treatment?

Which of the following are considered atmospheric air pollutants?

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