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
[{'content': 'Lymphocytes are located in each of the following tissues or organs EXCEPT one. The one exception is - \nSelect and explain. \nA. Brain, B. Spleen, C. Lymph nodes, D. Thymus gland', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]