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
Antigen binding site in immunoglobulin is 
Select and explain. 
A. Variable region, B. Hypervariable region, C. Constant region, D. all
B: Hypervariable region
Answer: B: Hypervariable region 
Explanation: Ans. is 'b' i.e., Hypervariable region