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
Immunoglobulin changes in variable region ? 
Select and explain. 
A. ldiotype, B. Isotype, C. A llotype, D. Epitope
A: ldiotype
Answer: A: ldiotype 
Explanation: Ans. is 'a' i.e., Idiotype