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: Medicine
[{'content': 'In one of the following condition cavities filled with\nfluid is seen in the centre of spinal cord: \nSelect and explain. \nA. Multiple sclerois, B. Syringo myelia, C. Tabes Dorsalis, D. Meningovascular syphilis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]