Buna-$N$ is a co-polymer of $1,3-$Butadiene and $\underline{X}$. What is $\underline{X}$?

Which one of the following structures represents the neoprene rubber?

Match List-$I$ with List-$II$ :
| List-$I$ | List-$II$ |
| :--- | :--- |
| $(a)$ Chloroprene | $(i)$ $CH_2=C(CH_3)-CH=CH_2$ |
| $(b)$ Neoprene | (ii) $CH_2=C(Cl)-CH=CH_2$ |
| $(c)$ Acrylonitrile | (iii) $[-CH_2-C(Cl)=CH-CH_2-]_n$ |
| $(d)$ Isoprene | (iv) $CH_2=CH-CN$ |
Choose the correct answer from the options given below :

The polymer $\begin{array}{*{20}{c}} {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,CH_3\,\,\,\,\,\,\,\,\,\,\,\,\,CH_3} \\ {\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\ {{( - CH_2 - C - CH_2 - C - )}_n} \\ {\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\ {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,CH_3\,\,\,\,\,\,\,\,\,\,\,\,\,CH_3} \\ \end{array}$ is formed from which monomer unit?

Terylene is used for making

Intermolecular forces in nylon-$6,6$ are