Polymer identification via linkage type

Steps:

• Examine the diagram for repeating units and connecting bonds.
• Identify the presence of -CONH- groups between monomers.
• Recognize -CONH- as the amide linkage from condensation of carboxylic acids and amines.
• Match to polyamide structure, like nylon.

Why A is correct:

• Polyamides feature amide bonds (-CONH-) in their backbone, formed by reaction between amine (-NH2) and carboxylic acid (-COOH) groups.

Why the others are wrong:

• B: Polyesters contain ester linkages (-COO-), not amides.
• C: Polyethene consists of C-C chains from ethene addition polymerization, lacking functional groups.
• D: Polysaccharides involve glycosidic bonds between sugar units, not amide linkages.

Final answer: A