This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cells and Tissues of Immune System, Subject name: Pathology
T - cells mature in? 
Select and explain. 
A. Bone marrow, B. Liver, C. Thymus, D. Lymph nodes
C: Thymus
Answer: C: Thymus 
Explanation: Ans is 'c' i.e., Thymus o T cell precursors arise in bone marrow (also in yolk sac & liver before birth) and migrate to the thymus. Maturity of T-cells takes place in the thymus (So, T cells arise in bone marrow and mature in thymus).o B cells originate as well as mature in bone marrow.