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': 'Which of the following is not true about water quality estimation - \nSelect and explain. \nA. Chlostridium spores indicate recent contamination, B. Not more than 5% samples should have coliforms, C. Sodium thiosulfate added to neutralize chlorine, D. Coliforms must not be detected in 100 ml sample', 'role': 'user'}, {'content': "Answer: A \nExplanation: Spores of Clostridium are capable of surviving in water for a longer time than the coliform group of organisms. The presence of Clostridium spores in the absence of coliform group suggest faecal contamination occurred at some remote time. Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 781", 'role': 'assistant'}]