The correct option is A Ester bonds
The three-dimensional structure of a protein is called its tertiary structure. The interactions between the R groups of amino acids make the secondary structure of protein fold and resemble a hollow ball, this is called the tertiary structure.
Hydrophobic interactions, H-bonds and electrostatic interactions are some of the weak interactions that stabilize the tertiary structure of proteins.
However, ester bonds are least likely to be involved in maintaining the tertiary structure of proteins.
Hence, the correct answer is option A.