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': 'Disinfection of water is not requihred if the source is from- \nSelect and explain. \nA. Tube well, B. Step well, C. Draw well, D. River', 'role': 'user'}, {'content': "Answer: A \nExplanation: Park's textbook of preventive and social medicine 23rd edition. *Tube wells are usually machine dug and may be several hundred metres deep. Deep wells furnish the safest water and are often the most satisfactory sources of water supply", 'role': 'assistant'}]