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Review unit: Part 1 (Exercise 1.1)


1. Water was first formed because of a chemical reaction between the gases hydrogen and oxygen.


2. As the temperatures dropped, a dense cloud released water in a downpour that lasted for 3,000 million years.


3. Most water is stored in the ice caps and glaciers.


4. The term aeration zone refers to the upper layer of the Earth.


5. The Sahara Desert has an underground water reservoir of about 200,000 cubic miles.


6. Most of our rainfall soaks into the ground.