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': 'Oxidation pond is used in treatment ? \nSelect and explain. \nA. Sewage, B. Effluent, C. Night soil, D. Sullage', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e.. Sew age", 'role': 'assistant'}]