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': 'Not seen in fecal pollution \nSelect and explain. \nA. Staphylococcus, B. Streptococcus, C. E.coli, D. Clostridium perfringens', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]