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': 'In β- thalassemia, there is \nSelect and explain. \nA. Excess chain, B. No β chain, C. No chain, D. Normal chains', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]