This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Forearm wrist and hand injuries, Subject name: Orthopaedics
[{'content': 'Axis of upper limb passes through \nSelect and explain. \nA. Capitulum, B. Trochlea, C. Olecranon, D. Radial styloid', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Mechanical axis It is defined as the straight line connecting the joint center points of the proximal and distal joints. The mechanical axis is always a straight line, whether in the frontal or sagittal plane. Anatomic axis The anatomic axis of a bone is the mid-diaphyseal line. The anatomic axis line may be straight in the frontal plane but curved in the sagittal plane, as in the femur. ref : maheswari 9th ed', 'role': 'assistant'}]