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': 'Spastic paraplegia can be caused by the following except - \nSelect and explain. \nA. Motor neuron disease, B. Chronic lead poisoning, C. Vitamin B12deficiency, D. Cervical spondylosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]