In post disaster phase, for ensuring safe water supply, it is advisable to have a Residual Chlorine Level of: (A) 0.3 mg/ litre, (B) 0.5 mg/ litre, (C) 0.7 mg/ litre, (D) 3.0 mg/ litre
Answer is C. Level of residual chlorine to be maintained in all water bodies in post-disaster phase is > 0.7 mg/l (> 0.7 ppm).