This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper limb, Subject name: Anatomy
[{'content': 'Carpometacarpal joint of thumb is \nSelect and explain. \nA. Saddle, B. Hinge, C. Ball and socket, D. Pivot', 'role': 'user'}, {'content': 'Answer: A \nExplanation: First carpometacarpal joint is only carpometacarpal joint which has separate joint cavity. Aicular surfaces are distal surface of trapezium and proximal surface of the base of the first metacarpal bone. B D Chaurasia 7th edition Page no: 161,162', 'role': 'assistant'}]