So, water is a compound that composed of two or more elements(hydrogen and oxygen)chemically joined together by chemical methods.
2006-10-23 16:37:22 補充:
The earth's crust, the ocean and the atmosphere provide us with all the resources we need for our survival, comfort and pleasure. The ocean(water) is cover over 70% of the surface area of the earth. Although we can produce the water by our techlogy, but it is rather expensive.