The primary pollutant that leads to photochemical smog is

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

List-$I$	List-$II$
$A$. Nitrogen oxides in air	$I$. Eutrophication
$B$. Methane in air	$II$. $pH$ of rain water becomes $5.6$
$C$. Carbon dioxide	$III$. Global warming
$D$. Phosphate fertilisers in water	$IV$. Acid rain

Choose the correct answer from the options given below:

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

List-$I$	List-$II$
$A$. Sulphate	$I$. Pesticide
$B$. Fluoride	$II$. Bending of bones
$C$. Nicotine	$III$. Laxative effect
$D$. Sodium arsinite	$IV$. Herbicide

Choose the correct answer from the options given below.

Match the following List-$I$ ($F^-$ ion concentration in drinking water) with List-$II$ (Effects on humans):

List-$I$	List-$II$
$(A)$ $< 1 \ ppm$	$(i)$ Harmful to bones
$(B)$ $> 2 \ ppm$	$(ii)$ Tooth decay
$(C)$ $> 10 \ ppm$	$(iii)$ Brown mottling of teeth

Then the correct match is:

Lead is considered as

Given below are two statements.
Statement $I:$ In polluted water,values of both dissolved oxygen and $BOD$ are very low.
Statement $II:$ Eutrophication results in a decrease in the amount of dissolved oxygen.
In the light of the above statements,choose the most appropriate answer from the options given below.