Which chemical bond specifically links amino acids together in a protein chain?

Hydrogen bonds between backbone amide hydrogens and carbonyl oxygens that covalently attach one amino acid to the next in a primary sequence of the polypeptide chain.

Glycosidic bonds connecting individual monosaccharide units into a long polymer that then attaches to amino acids to form proteins.

Phosphodiester bonds linking amino acid side chains through phosphate bridges in the primary structure.

Peptide bonds formed between the amino group of one amino acid and the carboxyl group of the next.