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': 'The main diagnostic test for hereditary spherocytosis is: \nSelect and explain. \nA. Osmotic fragility, B. Bone marrow study, C. Hemoglobin electrophoresis, D. Mutation study', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The presence of osmotic fragility is the main diagnostic test for hereditary spherocytosis. Ref: Harrisons principles of internal medicine, 18th edition, Page 875.', 'role': 'assistant'}]