Identify the incorrect statement.

$UV-$rays are non-ionizing type and are lethal due to their inactivation ability of:

Match the following columns:

Column-$I$	Column-$II$
$(a)$ Chipko Movement	$(1) \ 1987$
$(b)$ National Forest Policy of India	$(2) \ 1980$
$(c)$ Joint Forest Management	$(3) \ 1988$
$(d)$ Montreal Protocol	$(4) \ 1974$

What is found in photochemical smog?

The limit of $BOD$ prescribed by the Central Pollution Control Board $(CPCB)$ for the discharge of industrial and municipal wastewater into natural surface waters is

$A$ lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this:
$1.$ Lots of urea and phosphate fertilizer were used in the crops in the vicinity.
$2.$ The area was sprayed with $DDT$ by an aircraft.
$3.$ The lake water turned green and stinky.
$4.$ Phytoplankton populations in the lake declined initially,thereby greatly reducing photosynthesis.
Which two of the above were the main causes of fish mortality in the lake?