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: Medicine
Alpha chain disease is detected by - 
Select and explain. 
A. M component in serum, B. Jejunal biopsy, C. Light chain in lumen of jejunum, D. All of the above
B: Jejunal biopsy
Answer: B: Jejunal biopsy 
Explanation: None