Concept:A homopolymer is formed from only one type of monomer unit.
Explanation:Polyacrylonitrile is obtained by the polymerisation of only acrylonitrile monomers.
nCH2​=CHCN→[−CH2​−CH(CN)−]n​Since only acrylonitrile is used, it is a homopolymer.
The other options are copolymers because they are formed from more than one monomer.
Buna-N is made from butadiene and acrylonitrile.
Urea formaldehyde resin is made from urea and formaldehyde.
Polycarbonate is produced from bisphenol-A and phosgene.
Therefore, among the given options, only polyacrylonitrile qualifies as a homopolymer.
Answer:Option A: Polyacrylonitrile