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: Orthopaedics
[{'content': 'Investigation of choice for lumbar prolapsed disc \nSelect and explain. \nA. X-ray, B. CT Scan, C. MRI, D. Myelogram Patt', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Investigation of choice for PID at any level is MRI.', 'role': 'assistant'}]