This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2018, Subject name: Social & Preventive Medicine
[{'content': 'Value of free residual chlorine in Drinking water should be: \nSelect and explain. \nA. 0.2 mg/L, B. 0.3 mg/L, C. 0.4 mg/L, D. 0.5 mg/L', 'role': 'user'}, {'content': "Answer: D \nExplanation: It's should be minimum 0.5 mg/l (ppm) in drink water >= 1.0 mg /l swimming pool >=2.0 mg/l kill cyclops Measured by chloroscope", 'role': 'assistant'}]