Which of the following statements is $NOT$ true about Buna-$S$?

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 :

In Buna-$S$,the symbol $Bu$ stands for

Which of the following features is not true about low density polythene?

Discuss the main purpose of vulcanisation of rubber.

Which chromatography mode is used to determine the molecular mass of polymer substances?