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: Surgery
[{'content': 'The first step when doing a penumononectomy for cancer of the bronchus is to - \nSelect and explain. \nA. Ligate the pulmonary vein, B. Ligate pulmonary artery, C. Divide the bronchus, D. Perform lymphnode clearance', 'role': 'user'}, {'content': 'Answer: B \nExplanation: • Pneumonectomy is anatomically more straightforward than lobectomy (in carcinoma bronchus):\n• The pulmonary artery is first dissected, divided and sutured.\n• The pulmonary veins are then isolated, divided and sutured.\n• The main bronchus is divided so that no blind stump remains. The technique of stump closure is important if a bronchopleural fistula is to be avoided. The tissues are carefully handled and the stump is usually stapled.', 'role': 'assistant'}]