Concept:Nylon is a condensation polymer formed from a dicarboxylic acid and a diamine.Explanation:Nylon 6,6 is made by polymerising hexanedioic acid (adipic acid) with hexamethylenediamine.The acid component of the monomer pair is hexanedioic acid.Therefore, the relevant monomer among the options is hexanedioic acid.Answer:B. Hexanedioic acid