This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nerve Injuries - 1, Subject name: Orthopaedics
[{'content': "A patient can't extend his wrist after he has met with an accident. He has no sensory loss. Level at which the affected nerve is injured? \nSelect and explain. \nA. Spiral groove of humerus, B. Head of radius, C. Near medial epicondyle, D. Surgical neck of humerus", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Patient has wrist drop so radial nerve is involved, there can be sensory sparing in radial nerve injury.', 'role': 'assistant'}]