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
Softening is recommended when hardness of water is more than: 
Select and explain. 
A. 50mg/litre, B. 75mg/litre, C. 100mg/litre, D. 150mg/litre
D: 150mg/litre
Answer: D: 150mg/litre 
Explanation: Softening is recommended when hardness of water is more than 150 mg/L (> 3mEq/ L). Softening of water is done by Temporary hardness Permanent hardness Boiling Lime NaCo3 Permutit NaC03 Base exchange