Using Ahmed Khan's method in Bangalore,approximately $Q$ kilometers of road have been laid by the year $P$.

$A$ large number of fish suddenly die in a lake near a village. Which of the following could be the reason for this?
$(a)$ Excessive use of urea and phosphate fertilizers in nearby fields.
$(b)$ Spraying of $DDT$ in the entire area.
$(c)$ The lake water has turned green and murky.
$(d)$ The population of phytoplankton in the lake has decreased,reducing the photosynthetic capacity.
Which two of the above reasons are responsible?

The pesticide used as a preventive measure in buildings is

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

Which of the following refers to the increase in the concentration of a toxicant at successive trophic levels?

$NEERI$ is situated in