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: Social & Preventive Medicine
[{'content': "Which one of the following method is used for the estimation of the chlorine demand of water – \nSelect and explain. \nA. Chlorometer, B. Horrock's apparatus, C. Berkfeld filter, D. Double pot method", 'role': 'user'}, {'content': "Answer: B \nExplanation: Chlorine demand of water can be estimated by Horrock's apparatus.\nChlorine demand of water is the amount of chlorine that is needed to destroy bacteria, and to oxidize all the organic matter and ammoniacal substances present in water.\nIt is the difference between the amount of chlorine added to the water, and the amount of residual chlorine remaining at the end of a specific period of contact (usually 1 hr), at a given temperature and pH of water.\n\nInstrument\n\nHorrock's Apparatus\nChlorinator/ Chloronome\nChloroscope\n\nUtility\n\nChlorine demand estimation\nMixing or regulating dose of chlorine\nMeasuring residual level of chlorine\n\n\nBerkefield filter is a type of ceramic filter which is used for purifying water on small scale.\nThe Double Pot Method provides a constant dose of chlorine to well water during periods of emergency.", 'role': 'assistant'}]