What is the effect of $Pb$ (lead) on catalysts?

At the beginning of the twentieth century,forests covered about ........... percent of the land of India. By the end of the century,it shrunk to ............. percent.

$LPG$ cooking gas is

Match the following concentrations of $DDT$ in an aquatic food chain:

Column-$I$	Column-$II$
$(a)$ Small fish	$(1) \;25 \;ppm$
$(b)$ Zooplankton	$(2) \;2 \;ppm$
$(c)$ Fish-eating birds	$(3) \;0.5 \;ppm$
$(d)$ Large fishes	$(4) \;0.04 \;ppm$

If an agricultural field is liberally irrigated for a prolonged period of time,it is likely to face the problem of:

Match the following important dates/events related to environmental legislation in India:
$(i)$ Air (Prevention and Control of Pollution) Act
$(ii)$ Environment (Protection) Act
$(iii)$ Water (Prevention and Control of Pollution) Act $(1974)$