Monomer identification via polymer repeating units

Steps:

• Examine the polymer's partial structure for repeating linkages, such as ester or amide bonds.
• Compare to monomer 1, which contains functional groups that form those exact linkages upon condensation.
• Check monomer 2: its groups lead to different bond types, like ether instead of ester.
• Check monomer 3: it produces branched structures, unlike the linear chain shown.

Why A is correct:

• Monomer 1 alone undergoes step-growth polymerization to yield the precise repeating unit via dehydration, matching the structure per condensation polymer rules.

Why the others are wrong:

• B includes 2, which forms incompatible bonds (e.g., vinyl addition, not condensation).
• C includes 3, whose diol groups create side chains absent in the polymer.
• D uses only 2 and 3, both mismatched for the linear ester repeats.

Final answer: A