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
The gas which produces systemic toxicity without causing local irritation is – 
Select and explain. 
A. Ammonia, B. Carbon monoxide, C. Hydrocyanic acid, D. Sulfur dioxide
B: Carbon monoxide
Answer: B: Carbon monoxide 
Explanation: Carbon monoxide is a colorless, tasteless, non-irritative gas, which is produced due to incomplete combustion of carbon.