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: Dental
[{'content': 'Strength of sewage is best expressed by \nSelect and explain. \nA. E-coli count, B. Suspended particles, C. Chemical oxygen demand, D. Biological oxygen demand', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The most important test carried out on sewage. Sewage with a BOD value of:\n\n300mg/I (300 ppm) or above is termed as strong.\xa0\n100 mg/I (100 ppm) or below is termed as weak.', 'role': 'assistant'}]