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: Microbiology
[{'content': 'Immunoglobulin changes in variable region ? \nSelect and explain. \nA. ldiotype, B. Isotype, C. A llotype, D. Epitope', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Idiotype", 'role': 'assistant'}]