Polymer chain identification by repeating unit

Steps:

• Examine the repeating unit in the shown polymer chain.
• Compare the polymer's backbone and side groups to each monomer's structure.
• Identify the monomer that, upon polymerization, forms the exact linkage and sequence observed.
• Match the functional groups that react to produce the polymer's bonds.

Why D is correct:

• Monomer D contains the specific vinyl group and substituent that polymerize via addition to form the exact repeating -CH2-CH(R)- unit shown, per addition polymerization rules.

Why the others are wrong:

• A: Lacks the correct side chain, leading to a different R group in the polymer.
• B: Features a different double bond position, producing an unsaturated backbone not matching the chain.
• C: Involves condensation polymerization, resulting in ester linkages absent in the shown chain.

Final answer: D