Introduction:
Pure water is essential for the survival of all living organisms. It is important to understand where pure water comes from in order to ensure its availability and conservation.

Main Body:
Rain:
Rain is the natural source of pure water. When water evaporates from various water bodies, such as oceans, lakes, and rivers, it forms clouds. These clouds then release water in the form of rain. Rainwater is considered pure because it does not contain any impurities or contaminants. However, as it falls through the atmosphere, it can pick up some pollutants and become slightly acidic.

Sea:
The sea is not a natural source of pure water. Sea water is salty and cannot be consumed directly by humans or used for irrigation. However, through the process of desalination, which involves removing the salt and other impurities from sea water, it is possible to obtain pure water. Desalinated water is often used in areas where freshwater sources are scarce.

River:
Rivers are not a natural source of pure water. River water contains various impurities such as sediments, minerals, and pollutants. However, with proper treatment, river water can be purified and made safe for consumption. Water treatment plants use processes like filtration, coagulation, and disinfection to remove impurities and ensure the water is safe to drink.

Wall:
A wall is not a natural source of pure water. Walls are made of materials such as bricks, concrete, or wood, which do not produce water. However, walls can be a part of man-made structures like dams or reservoirs, which can store and distribute water.

Conclusion:
In conclusion, rain is the natural source of pure water. Other sources of water, such as the sea and rivers, may contain impurities that need to be removed through various processes to obtain pure water. It is important to understand the sources of water and their quality in order to ensure the availability of safe and clean water for drinking and other purposes.

Rain