Water never stops moving. Snow and rain fall to the earth from the sky. That water runs down into rivers and lakes, and sometimes it makes waterfalls. Finally, the water runs out into the sea.

How does water get up into the sky.'? It evaporates (蒸发) from the ground. The sun changes water into gas, and it goes up to make clouds. There, the cycle (循环) begins again.

     The cycle tells us that water may evaporate and change into clouds, but it’s still water. The water you drink could be the same water that dinosaurs drank!

     But too much of our water today has been polluted. Our water may never go away, but a lot of it is becoming too dirty for us to drink!

    1. Which of the following can be filled in the boxes below to show how water cycles?

A. (1) clouds, (2) rain, (3) rivers, (4) sea

B. (1) rivers, (2) clouds, (3) rain, (4) sea

C. (1) clouds, (2) rivers, (3) sea, (4) rain

D. (1) rivers, (2) sea, (3) rain, (4) clouds

2. Water evaporates because________

     A. it never changes

     B. it never stops moving

C. the sun turns it into gas

D. it runs into the sea

3. The underlined sentence means that________

A. water may change into other forms, but it’s still water

B. water may go away

C. there are still dinosaurs on the earth today

D. dinosaurs drink water as we do

4. The water problem we are facing now is that

A. too much of it has evaporated

B. a lot of water flows into the sea

C. a lot of water has been polluted

D. water can′t be recycled

5. The best tide for this passage is

A. Water pollution

B. How water changes into clouds

C. Evaporation

D. Water cycle