This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anesthesia Machine, Subject name: Anaesthesia
Gas cylinder with single pin index - 
Select and explain. 
A. Oxygen, B. Air, C. Nitrogen, D. Entonox
D: Entonox
Answer: D: Entonox 
Explanation: Ans. is 'd' i.e., Entonox GasPin indexOxygen2,5Nitrous oxide3,5Cyclopropane3,6Air1,5Nitrogen1,4Entonox (50% O2 + 50% N2O)Single central (7)Carbon dioxide (< 7[?]5%)2,6Carbon dioxide (>7[?]5%)1,6