HOOC(CH2)4COOH,H2N(CH2)4NH2
HOOC(CH2)6COOH,H2N(CH2)4NH2
HOOC(CH2)6COOH,H2N(CH2)6NH2
HOOC(CH2)4COOH,H2N(CH2)6NH2
Nylon 66 is made of two monomers each containing 6 carbon atoms, hexamethylenediamine and adipic acid, which give nylon 66 its name. Hexamethylene diamine ↓H2N−(CH2)6−NH2 + Adipic acid ↓HOOC−(CH2)4−COOH. Hence, option D is correct.