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: Physiology
Primary sites of lymphocyte production are 
Select and explain. 
A. Bone marrow and Thymus, B. Spleen and Lymph nodes, C. Lymph nodes and mucosa associated lymphoid tissue, D. Spleen and mucosa associated lymphoid tissue
A: Bone marrow and Thymus
Answer: A: Bone marrow and Thymus 
Explanation: None