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: Anaesthesia
[{'content': 'Pneumothorax is a complication of \nSelect and explain. \nA. Axillary block, B. Brachial plexus block, C. Epidural block, D. High Spinal block', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Brachial Plexus block Brachial plexus block with interscalene approach provides most intense anesthesia in C5-C7 dermatomes and least intense in C8-T1 (ulnar nerve) area.', 'role': 'assistant'}]