Matching polymer structure to diamine and diacid monomers

Steps:

• Examine the polymer's repeating unit for amide linkages and atoms between nitrogens and carbonyls.
• Identify the diamine segment as the part between amide nitrogens (e.g., direct N-N bond).
• Identify the diacid segment as the part between carbonyls (e.g., direct C-C bond).
• Compare to monomer options to find exact matches without extra carbon chains.

Why C is correct:

• Hydrazine (H₂N-NH₂) and oxalic acid (HOOC-COOH) condense to form -[NH-NH-CO-CO]- repeating units via amide bonds, as defined in polyhydrazide synthesis.

Why the others are wrong:

• A introduces -CH₃- groups, creating -NH-CH₃-NH-CO-CH₃-CO- units mismatched to the structure.
• B adds -CH₂- groups, yielding -NH-CH₂-NH-CO-CH₂-CO- units with extra carbons.
• D includes -CH₂-CH₂- chains, producing -NH-CH₂-CH₂-NH-CO-CH₂-CH₂-CO- units too long for the structure.

Final answer: C