Which of the following protects life on earth from harmful effects of $UV$ radiations from the sun?

Give two names of herbicides.

$BOD$ values (in $ppm$) for clean water $(A)$ and polluted water $(B)$ are expected respectively:

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

The consequence of global warming may be the following:

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