Which of the following methods can be used to control water pollution?

Which of the following statements about smog is/are correct?
$(i)$ Smog formed on sunny days contains oxidizing molecules.
$(ii)$ Photochemical smog contains many reactive molecules.
$(iii)$ The main polluting components of smog are oxides of carbon.
$(iv)$ The presence of carbon monoxide in air leads to the formation of ozone in smog.

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.

Biochemical oxygen demand $(BOD)$ value can be a measure of water pollution caused by organic matter. Which of the following statements is correct?

The structure of all living organisms on Earth is known as ............

The gaseous component present in the troposphere is ...... .