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': 'Ground water has the following advantages except - \nSelect and explain. \nA. Likely to be free from pathogenic organisms, B. Usually requires no treatment, C. Supply is likely to be ceain during dry season, D. Likely to be hard', 'role': 'user'}, {'content': "Answer: D \nExplanation: Groundwater sources are wells and springs. Groundwater is the cheapest and most practical means of providing water in small quantities. Groundwater is superior to surface water because It is likely to be free from pathogenic organisms. it usually requires no treatment supply is likely to be ceain even in dry seasons less subject to contamination. The disadvantages are high in mineral content(salts of magnesium and calcium which render water hard) - it requires pumping or some arrangement to lift the water. The hardness of water is caused by salts of calcium and magnesium( calcium bicarbonate, magnesium bicarbonate, calcium sulphate, magnesium sulphate). Park's textbook of Community Medicine.edition 25. page no: 768", 'role': 'assistant'}]