This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Joint disorders, Subject name: Orthopaedics
[{'content': 'Earliest investigation for diagnosis of Ankylosing spondylitis- \nSelect and explain. \nA. MRI STIR sequence, B. Bone scan, C. CT scan, D. X-ray', 'role': 'user'}, {'content': 'Answer: A \nExplanation: mri stir sequence most precise investigation of choice in patients with ankylosing spondilitis ref : maheswari 9th ed', 'role': 'assistant'}]