This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and Health, Subject name: Social & Preventive Medicine
Residual chlorine in drinking water should be- 
Select and explain. 
A. 0.5 mg /L, B. 0.7 mg/L, C. 1 mg/L, D. 2 mg/L
A: 0.5 mg /L
Answer: A: 0.5 mg /L 
Explanation: Ans. is 'a' i.e., 0.5 mg /L Water typeRecommendedResidual chlorine levelContact periodDrinking water> 0.5 mg per litre (ppm)1 hourWater bodies, post disaster> 0.7 mg per litre (ppm)1 hourSwimming pool sanitation>1.0 mg per litre (ppm)1 hour