The monomer used to make polyvinyl chloride, PVC, is

Explanation

Chloroethene, also called vinyl chloride, has the double bond needed for addition polymerisation and carries the chlorine that gives PVC its rigidity and flame resistance. Chloroethane is saturated and so cannot polymerise by addition, which is the distractor to watch for. PVC is used for pipes, cable insulation and flooring, and plasticisers are added when a flexible product is wanted.