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
All are true regarding nitrous oxide except 
Select and explain. 
A. Nitrous oxide is good analgesic agent., B. Nitrous oxide cylinder is blue coloured, C. Inhibits thymidylate synthetase enzyme, D. Good agent to use in pan retinal photocoagulation
D: Good agent to use in pan retinal photocoagulation
Answer: D: Good agent to use in pan retinal photocoagulation 
Explanation: Nitrous oxide being combustible agent, is contraindicated in laser surgeries.