This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Water, Subject name: Social & Preventive Medicine
Hardness of water is due to all except: 
Select and explain. 
A. Sulfates, B. Chlorides, C. Nitrates, D. Phosphates
D: Phosphates
Answer: D: Phosphates 
Explanation: Hardness of water Temporary hardness (carbonate hardness) is due to calcium & magnesium salts of bicarbonates. Permanent hardness (non - carbonate hardness) is due to calcium & magnesium salts of sulfates, chlorides, nitrates. Four main compounds causing hardness: calcium bicarbonates, magnesium bicarbonates, calcium sulfates, magnesium sulfates.