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
[{'content': "Rebreathing systems are WE \nSelect and explain. \nA. To & fro system, B. Circle system, C. Water's system, D. Mapleson F", 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Mapleson F - Calcium hydroxide is the main component of both sodalime (94%) and baralimeQ (80%). - Ba(OH)2 is not a constituent of soda lime, it is used in baralime. Water (of crystalization) is used to produce hardening in baralimeQ. - Clayton, mimosaQ, ethyl violet, phenolphthalein & ethyl orange are indicators.', 'role': 'assistant'}]