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
Anaesthetic circuit that prevents rebreathing of CO2 – 
Select and explain. 
A. Magil's circuit, B. Mapleson D circuit, C. Ayre's piece, D. Circle system
D: Circle system
Answer: D: Circle system 
Explanation: You all know, amongst the given options only circle system is rebreathing system. It is quite obvious, CO2 must be eliminated from the exhaled air before rebreathing to prevent hypercapnia. Therefore, rebreathing system has a CO2 absorbent that absorbs CO2 and prevents CO2 rebreathing. Don’t get confuse by name (rebreathing system), there is rebreathing of exhaled gases after absorption of CO2.