This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthetic equipments, Subject name: Anaesthesia
Pin code index of N2O is 
Select and explain. 
A. 1,6, B. 2,5, C. 2,6, D. 3,5
D: 3,5
Answer: D: 3,5 
Explanation: PIn index provides prevention of wrong attachments of cylinders . N20 - 3 ,5 O2 - 2 , 5 C02 (Gas) - 1 ,6 . ( Liquid below 88F ) 2 , 6 ; Cyclopropane 3 , 6 .