This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'B cell maturation takes place in - \nSelect and explain. \nA. thymus, B. Lymph node, C. Bone marrow, D. Spleen', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The key cells in our immune system are lymphocytes known as B cells and T cells, which originate in our bone marrow. After T cells fuher develop in our thymus. Reff: www.mayoclinic.com', 'role': 'assistant'}]