Which of the following undergoes polymerization to form $PVC$?

Ziegler-Natta catalyst is used for which type of reaction?

Which of the following is a Ziegler-Natta catalyst?

The following structure represents a subunit of a hydrocarbon polymer that may be prepared by a radical polymerization method. Identify the monomer that has been polymerized to make this polymer chain.

The polymer $X$ consists of linear molecules and is closely packed. It is prepared in the presence of triethylaluminium and titanium tetrachloride under low pressure. The polymer $X$ is -

The monomers of buna-$S$ rubber are