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 adults, cervical instability most commonly results from \nSelect and explain. \nA. A rotational injury, B. A flexion extension injury, C. Degenerative disc disease, D. Increased ligamentous laxity', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Cervical instability, defined as AP subluxation of more than 3.5 mm or sagittal angulation greater than 20deg on flexion-extension radiographs, most commonly results from disc degeneration, with its attendant changes in the facet joints and loss of ligamentous suppo. Ref: internet sources', 'role': 'assistant'}]