This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'Not seen in faecal pollution - \nSelect and explain. \nA. Staphylococcus, B. Streptococcus, C. E. Coli, D. Clostridium perfringens', 'role': 'user'}, {'content': "Answer: A \nExplanation: The primary bacterial indicators of contamination of water are the coliform group. Supplementary indicators include faecal streptococci and sulphite-reducing clostridia(C.perfringens) Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 780,781", 'role': 'assistant'}]