Which from following polymers contains - CO - NH - linkage ?

Step-by-step solution

The -CO-NH- linkage corresponds to an amide functional group found in polyamides and related polymers. Glyptal is a polyester formed from phthalic acid and ethylene glycol, containing ester linkages ( -COO- ) but no amide groups. Thermocol (expanded polystyrene) is an addition polymer of styrene, lacking heteroatom functional groups. Buna-N is a copolymer of 1,3-butadiene and acrylonitrile; though acrylonitrile contains a nitrile group ( -CN ), polymerization yields carbon-carbon backbone chains without amide linka