This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment, Subject name: Social & Preventive Medicine
[{'content': 'Which of the following is a bacteriological indicator of water quality? \nSelect and explain. \nA. Staphylococcus aureus, B. Clostridium tetani, C. E.coli, D. Yersinia pestis', 'role': 'user'}, {'content': "Answer: C \nExplanation: Coliform organisms: Primary & most reliable bacterial indicator for water quality. E. coli is most impoant coliform indicator. Fecal streptococci: Indicate 'recent contamination of water'. Clostridium perfringens: Indicate 'remote contamination of water'.", 'role': 'assistant'}]