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': 'The gas which produces systemic toxicity without causing local irritation is – \nSelect and explain. \nA. Ammonia, B. Carbon monoxide, C. Hydrocyanic acid, D. Sulfur dioxide', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Carbon monoxide is a colorless, tasteless, non-irritative gas, which is produced due to incomplete combustion of carbon.', 'role': 'assistant'}]