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': 'A lady having flexion at proximal interphalyngeal joint and hyperextension at distal interphalyngeal joint of index finger is called- \nSelect and explain. \nA. Boutonniere deformity, B. Swan neck deformity, C. Wind swept deformity, D. Z deformity', 'role': 'user'}, {'content': 'Answer: A \nExplanation: ref : maheswari 9th ed', 'role': 'assistant'}]