A) Nylon has same amide linkage as in protein.
Nylon-66 is a polymer made from hexanedioyl chloride and hexane-1,6-diamine.
The repeating unit in Nylon-66 is 14 atoms long.
It has an amide linkage
(Adapted from Biology)
A protein is a polymer of different amino acids with general formula
(Adapted from AUS-e-TUTE)
The repeating unit in the protein chain is a 3-atoms-long amino acid. It has an amide linkage at each end (marked by the red arrows).
However, the amino acids can be arranged in seemingly random order, so there are no repeating units other than the general amino acids.