Which of the following statements about protein structure is correct?A. Proteins consisting of one polypeptide can have quaternary structure.B. The formation of a disulfide bond in a protein requires that the two participating cysteine residues be adjacent to each other in the primary sequence of the protein.C. The stability of quaternary structure in proteins is mainly a result of covalent bonds among the subunits.D. The denaturation of proteins always leads to irreversible loss of secondary and tertiary structure.E. The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain.