What’s the problem the world is now facing? The world is not only hungry but it

The world is not only hungry but it is also (16)thirsty for water. This may seem strange to you for nearly 70% of the earth’s surface is covered with water. But about 97% of that huge amount is sea water. Man can only drink and use (17)the three percent—the fresh water that comes from rivers, lakes and (18)underground. And we cannot even use all of it, (19)because some of it is polluted. However the small amount of fresh water which is sometimes replaced by rainfall is still enough for us now. But our need for water is increasing rapidly almost day by day. Only by taking steps now can we avoid the serious water shortage in the future. One way is to make use of sea water by (20)removing the  salt,  which is  already in use in many parts of the world.