This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Spinal Injuries, Subject name: Orthopaedics
[{'content': 'In Spondylolisthesis, which of the following is NOT useful investigation? \nSelect and explain. \nA. Anteroposterior X-ray, B. Lateral view X-ray, C. CT, D. MRI', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (a)-AP view will show changes only in last stages-inverted Napoleon hat sign all other are more important for diagnosis and management. CT and MRI are required in all cases.', 'role': 'assistant'}]