Answer:
Cold treatment.
Step-by-step explanation:
The proteins is the biomolecule made of the alpha amino acids linked through the peptide bond. Protein acts as the main building block of the individual's body.
The protein when subjected to the different physical and chemical treatment may result in the loss of the biological activity of the protein. This is known as denaturation. Cold treatment do not result in the change in structure of the protein and do not cause any denaturation.
Thus, the answer is option (a).