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': 'Marker of fecal contaminatin is - \nSelect and explain. \nA. A scaris, B. E. coli, C. guinea worm presence, D. Balantidium coli', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., E. coli", 'role': 'assistant'}]