World Environment Day is celebrated on

Select the correct option for 'Ecosan'.

In a pond near a village,a large number of fish suddenly die. Which of the following could be the reason for this?
$(a)$ Large amounts of urea and phosphate are used as fertilizers in nearby fields.
$(b)$ $DDT$ was sprayed in the entire area.
$(c)$ The pond water has become green and dirty.
$(d)$ The population of phytoplankton in the pond has decreased,reducing the photosynthetic capacity.
Which two of the above reasons are responsible?

Arrange $CFC, CH_4, N_2O$ and $CO_2$ in decreasing order according to their contribution in the greenhouse effect.

Select the appropriate option for $FOAM$.

More than $70\%$ of the world's freshwater is contained in $............$.