This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Absence of lymph nodes is characteristic of \nSelect and explain. \nA. Brain, B. Liver, C. Lung, D. Placenta', 'role': 'user'}, {'content': "Answer: A \nExplanation: The brain, pa of the central nervous system, has blood vessels but has been thought to lack lymphatic vessels, as they've never been found in humans . Ref - researchgate.net", 'role': 'assistant'}]