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: Biochemistry
[{'content': 'True about Ig gene rearrangement & Ig diversity: \nSelect and explain. \nA. Somatic mutations theory, B. DNA rearrangement, C. Appropriate class switching, D. All', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A, B, C i.e. Somatic mutations theory, DNA rearrangement, Appropriate class switching', 'role': 'assistant'}]