What is acid rain? Give the name of the gases responsible for the acid rain.

Which of the following statements are correct?
$A$. Ocean is a sink for $CO_2$.
$B$. Greenhouse effect causes lowering of the temperature of the earth's surface.
$C$. To control $CO$ emission by automobiles,usually catalytic converters are fitted into exhaust pipes.
$D$. $H_2SO_4$,herbicides,and insecticides form mist.

When the biosphere becomes an environment useful to humans,what is it called?

Match the following metals in drinking water with their maximum prescribed concentration in $ppm$:

List-$I$ (Metal)	List-$II$ (Concentration in $ppm$)
$A$. $Mn$	$I$. $0.05$
$B$. $Zn$	$II$. $5.0$
$C$. $Cd$	$III$. $0.005$
$D$. $Cu$	$IV$. $3.0$

Which free radical is formed when chlorine monoxide free radical reacts with an oxygen atom?

Acid rain occurs due to atmospheric pollution of