Water retuns on earth's surface from the atmosphere by the process of:

1. combustion
2. respiration
3. photosynthesis
4. condensation

Spring water is classified as:

1. surface water
2. above surface water
3. underground water
4. none of these

What is the importance of water cycle in nature.

Name the two gases from which water is formed. What is the chemical composition of these two gases in water? Give the molecular formula of water.