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: Medicine
[{'content': 'Basic defect in HbS is - \nSelect and explain. \nA. Altered function, B. Altered solubility, C. Altered stability, D. Altered O2 binding capacity', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]