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: Pathology
[{'content': 'The most common structural red cell defect without Hb abnormality is - \nSelect and explain. \nA. Elliptocytosis, B. Spherocytosis, C. Poikilocytosis, D. Sickle cell disease', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]