Repeating Unit of Polyvinyl Chloride (PVC)

Steps:

• PVC forms by addition polymerization of vinyl chloride (CH₂=CHCl).
• The double bond opens, linking monomers into -[CH₂-CHCl]-n chain.
• Examine each option for this exact repeating unit.
• Select the structure matching -CH₂-CHCl- without branches or errors.

Why A is correct:

• It shows the -CH₂-CHCl- repeating unit, as defined by PVC's structure from vinyl chloride polymerization.

Why the others are wrong:

• B: Depicts -CH₂-CH₂-, the repeating unit of polyethylene, not PVC.
• C: Represents the vinyl chloride monomer (CH₂=CHCl), not the polymer chain.
• D: Includes incorrect substitution, like a phenyl group, unrelated to PVC.

Final answer: A