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': 'During cesarean section under general endotracheal anaesthesia, venous air embolism \nSelect and explain. \nA. Is associated with high end-tidal CO2, B. Should be treated with nitrous oxide, C. Is associated with expired nitrogen, D. Induces severe hypertension', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Expired Nitrogen is the most sensitive venous-air embolism detection method, as the largest component of air is nitrogen.', 'role': 'assistant'}]