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': 'HbA2 concentration in thalassemia trait is - \nSelect and explain. \nA. 1, B. 1-2.5, C. 2.5-3.5, D. >3.5', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]