Pesticides with very low biodegradation but strong affinity for fatty tissues are:

Consider the following reasons for the massive fish mortality observed in a lake near a village within a few days:
$(1)$ Excessive use of urea and phosphate fertilizers in nearby crops.
$(2)$ Spraying of $DDT$ using aircraft.
$(3)$ The lake water turned green and foul-smelling.
$(4)$ Initial decrease in phytoplankton in the lake leads to a maximum decrease in photosynthesis.
Which of the above reasons are responsible for the massive fish mortality?

In Maharashtra,a $24$-hour toll-free helpline number $1926$ has been set up to provide information regarding . . . . . . .

In the town of Arcata,the local people,in collaboration with biologists from $...........$,developed an integrated wastewater treatment process within a natural system.

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

$A$ : Montreal Protocol suggested the reduction of $ODS$.
$R$ : $A$ landmark international agreement taken in Earth summit held at Rio de Janeiro.