Highly polluted water could have a $BOD$ value of: (in $ppm$)

What is green fuel?

Name the acids present in acid rain and state their sources in rainwater.

Which of the following statements are correct?
a) $F^{-}$ ion concentration above $2 \ ppm$ causes brown mottling of teeth
b) The maximum limit of nitrate in drinking water is $400 \ ppm$
c) Depletion of ozone layer leads to cataract and skin cancer
d) The irritant red haze in the traffic is due to oxides of sulphur

Eutrophication causes:

Which of the following factors will be responsible for skin-related diseases in the coming years?