The correct answer is b peptide bonds.
Peptide bonds are the covalent bonds that link amino acids together in a protein, forming the primary structure. They are vital for building the protein itself but do not influence the protein’s tertiary structure, which is the overall 3D shape formed by various interactions between the side chains of the amino acids. In contrast, ionic bonds, hydrogen bonds, bonds between sulfur atoms (disulfide bonds), and hydrophobic interactions all play key roles in stabilizing the tertiary structure by facilitating different types of non-covalent interactions that help fold the protein into its functional form.