This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'Keratin in skin is softer than keratin in nail because keratin in skin has: \nSelect and explain. \nA. Less number of disulphide bonds, B. Less number of salt bridges, C. High sodium content, D. Different affinity for water', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Less number of disulphide bondsKeratin in skin is softer than keratin in nail, horn & hooves because skin keratin has less number of disulfide bondsQ between Cys residues of adjacent polypeptide chains.', 'role': 'assistant'}]