Social & Preventive Medicine Amount of free residual chlorine in drinking water: September 2007, March 2010 A 0.1 mg/L B 0.5 mg/L C 1.0 mg/L D 1.5 mg/L 💡 Explanation Amount of free residual chlorine in drinking water: September 2007, March 2010 ✓ Correct Answer: B. 0.5 mg/L