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': 'In post disaster phase, for ensuring safe water supply, it is advisable to have a Residual Chlorine Level of \nSelect and explain. \nA. 0.3 mg/ litre, B. 0.5 mg/ litre, C. 0.7 mg/ litre, D. 3.0 mg/ litre', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Level of residual chlorine to be maintained in all water bodies in post-disaster phase is > 0.7 mg/l (> 0.7 ppm).', 'role': 'assistant'}]