Solution

Each of two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties called isomer.

An addition polymer is a polymer that forms by simple linking of monomers without the co-generation of other products.

Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner.

Polyvinyl chloride is a polymer produced by addition polymerization of the vinyl chloride monomer $$(CH_2-CHCl)$$. So, they neither be isomers nor allotropes.

Hence. option $$B$$ is correct.