What is $DDT$ among the following?

Which of the following is an air pollutant?

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.

Pollution is a change in physical,chemical or biological characters of our land and water that may be

Match List-$I$ with List-$II$ :

List-$I$	List-$II$
$a$. Biochemical oxygen demand	$i$. Oxidising mixture
$b$. Photochemical smog	$ii$. Stratospheric cloud
$c$. Classical smog	$iii$. Organic matter in water
$d$. Ozone layer depletion	$iv$. Reducing mixture

Choose the correct answer from the options given below:

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$A$. Sulphate $(> 500 \ ppm)$	$I$. Methemoglobinemia
$B$. Nitrate $(> 50 \ ppm)$	$II$. Brown mottling of teeth
$C$. Lead $(> 50 \ ppb)$	$III$. Laxative effect
$D$. Fluoride $(> 2 \ ppm)$	$IV$. Kidney damage

Choose the correct answer from the options given below.