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': 'Which of the following gene mutation occurs in cleidocranial dysplasia: \nSelect and explain. \nA. CDFA1 gene., B. CBFA1 gene., C. CBFA2 gene., D. None.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]