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: Unknown
The lineage specific marker for B cells is 
Select and explain. 
A. CD 19, B. CD 20, C. CD 21, D. CD 22
A: CD 19
Answer: A: CD 19 
Explanation: Lineage specific B cell marker is CD 19. However on IHC the best marker is CD 20. CD 21 is the receptor for EBV