This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper limb nerve supply and brachial plexus, Subject name: Anatomy
[{'content': 'The given clinical condition is due to involvement of nerve which is branch from which pa of brachial plexus \nSelect and explain. \nA. Root, B. Trunk, C. Division, D. Cord', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Diagnosis - winging of scapula - long thoracic nerve - branch from root of brachial plexus', 'role': 'assistant'}]