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 stored in liquid form is: 
Select and explain. 
A. Carbon dioxide, B. Nitrous oxide, C. Cyclopropane, D. Oxygen
B: Nitrous oxide
Answer: B: Nitrous oxide 
Explanation: Nitrous oxide