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': 'In ankylosing spondylitis, radiological change are first seen in - \nSelect and explain. \nA. Sacro-iliac joints, B. Intervertebral ligament, C. Vertebral bodies, D. Intervertebral discs', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]