This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Purest water in nature is 
Select and explain. 
A. Rain water, B. River water, C. Deep well, D. Impounding reservoirs
A: Rain water
Answer: A: Rain water 
Explanation: Rain : Is the prime source of all water and is the ‘purest form of water in nature.’
Chemically, it is very soft water : contains traces (0.0005%) of solids Gibraltar depends on rain water as a source of supply.