This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'According to Chandler’s index water containing 200-250 eggs should be considered as \nSelect and explain. \nA. Safe, B. Mild pollution, C. Dangerous, D. Public health problem', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]