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
According to the WHO , what is the minimum bacteriological standard for drinking water - 
Select and explain. 
A. All the samples should not contain coliform organisms, B. 3 consecutive samples of water should not contain any coliforms, C. 3 coliforms in a 100 ml water, D. 1 coliform in a 100 ml water
A: All the samples should not contain coliform organisms
Answer: A: All the samples should not contain coliform organisms 
Explanation: Must not detect E. coli or thermotolerant bacteria in any 100 ml sample. Total coliform bacteria should be nil in any 100 ml sample Park's Textbook of Preventive and Social Medicine, 25th edition, Page No. 782