Identify the polymer used to prepare plastic bottles needed to store cooking oil.

In polymer Buna-$S$,'$S$' stands for :-

$A$ polymer with high chemical stability has a melting point $(M.P.)$ of $327\ ^\circ C$ and the density of a completely crystalline sample is $2.3\ g/cm^3$. It is:

Give reason: Why is the molecular mass of a polymer always expressed as an average?

The polymer chains are held together by hydrogen bonding in a polymer $X$. Polymer $X$ is formed from monomers $Y$ and $Z$. What are $Y$ and $Z$ ?

$CH_2=CH-C_6H_5$	$H_2N(CH_2)_6NH_2$	$CH_2=CH-CH=CH_2$	$CH_2=CH-CN$	$HO_2C(CH_2)_4CO_2H$
$A$	$B$	$C$	$D$	$E$

Consider the following sequence of reactions.
$2 CH_3Cl + Si$ $\xrightarrow[573 \ K]{Cu} X$ $\xrightarrow{H_2O} Y$ $\xrightarrow{\text{Polymerization}} Z$
The repeating structural unit in $Z$ is