11.  Because the water soarce on earth is so limited, the first we must make use of it, we should not waste it, the second we should do is that we must develop our technique to use the water we couldn't use before, just as polluted water and iceburg in the antlantic oceaon .

12.  Factories can take steps to make polluted water refreshed and used .

13.  Some experts think that we should purity polluted water, and go on using them.

14.  Moreover, we May refresh used water and polluted water and make them to be used again.

15.  The polluted water can't be used by people.

16.  Every factory should clean the polluted water before it was put into river or lake .

17.  We must reused the polluted fresh water in other way, and we turn polluted water into fresh water.

18.  You can see polluted water in rivers nere factories or in the coutryside .

19.  We should also do our best to make the polluted water clean.

20.  Second, man must deal with the pollution to purify the polluted water.