38. Regarding the thermodynamic changes during protein denaturation and refolding, which of the following statements is correct? (A) When urea is used to denature a protein, the overall entropy of the system decreases. (B) When a protein refolds into its native structure, the entropy of the polypeptide chain itself decreases. (C) Protein denaturation treatments mainly destroy disulfide bonds and do not affect intermolecular hydrogen bonds. (D) Intrinsically disordered proteins maintain an extremely compact 3D structure both before and after denaturation.