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
Gas is filled as liquid in cylinder in – a) O2b) CO2 c) N2Od) Cyclopropanee) Halothane 
Select and explain. 
A. bcd, B. d, C. ab, D. ac
A: bcd
Answer: A: bcd 
Explanation: Oxygen, nitrogen, air and helium → Gaseous form
Nitrous oxide, carbon dioxide and cyclopropane → Liquid in equilibrium with saturated vapour.