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: Unknown
[{'content': 'False statement regarding chlorination of water: \nSelect and explain. \nA. Water should be free from turbidity, B. Chlorine demand of water should be estimated, C. Contact period of at least 2 hours is essential, D. Recommended residual free chlorine level is 0.5 mg/liter', 'role': 'user'}, {'content': 'Answer: C \nExplanation: (Refer: K. Park’s Textbook of Preventive and Social medicine, 24th edition, pg no: 765, 766)\nRecommended minimum contact period is 1 hour for chlorination\nPrinciples of chlorination\n\nWater should be clear, turbid free\nChlorine demand should be estimated, which is the amount of chlorine needed to destroy bacteria, oxidize all organic matter, neutralise all ammoniacal substances in water\nBreakpoint chlorination – The point a which chlorine demand of the water is met Free chlorine begins to appear in water, if further chlorine is added beyond breakpoint\nRecommended minimum\xa0 contact period is 1 hour for chlorination\nRecommended Residual chlorine for drinking water is 0.5 mg / litre\nFor water bodies, post disaster – 0.7 mg / litre\nFor swimming pool sanitation, it is 1.0 mg/ litre', 'role': 'assistant'}]