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': 'In Beta thalassemia, the most common gene mutation is - \nSelect and explain. \nA. Intron 1 inversion, B. Intron 22, C. 619 bp deletion, D. 3.7 bp deletion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]