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': 'A solitary bone cyst is most common in the - \nSelect and explain. \nA. Upper end of humerus, B. Lower end of humerus, C. Upper end of fibula, D. Lower end of femur', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Simple bone cysts commonly occurs at metaphysis of long bones.\nMost common site is proximal humerus (55%), followed by proximal femur (26%).', 'role': 'assistant'}]