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
[{'content': 'The minimum recommended concentration of free chlorine in drinking water at the end of one hour (mg/L) is - \nSelect and explain. \nA. 0.1, B. 0.5, C. 1, D. 1.5', 'role': 'user'}, {'content': "Answer: B \nExplanation: The minimum recommended amount of residual chlorine is 0.5 mg/L. Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 774", 'role': 'assistant'}]