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
In sickle cell anaemia defect is in which chain ? 
Select and explain. 
A. a-chain, B. B-chain, C. Both the chains, D. None of these
B: B-chain
Answer: B: B-chain 
Explanation: Ans. is 'b' i.e., n-chain