Scientists are trying to make the deserts into good land again. They want to bring water to the deserts， so people can live and grow food. They are learning a lot about the deserts. But more and more of the earth is becoming desert all the time. Scientists may not be able to change the desert in time.

Why is more and more land becoming desert？Scientists think that people make deserts. People are doing bad things to the earth.

Some places on the earth don’t get much rain. But they still don’t become deserts. This is because some green plants are growing there. Small green plants and grass are very important to dry places. Plants don’t let the sun make the earth even drier. Plants do not let the wind blow the dirt away. When a bit of rain falls，the plants hold the water. Without plants，the land can become desert more easily.

1.Deserts ＿＿＿＿＿＿＿＿ .

2.Small green plants are very important to dry places because ＿＿＿＿＿＿.

3.Land is becoming desert little by little because ＿＿＿＿＿＿.

4.After reading this passage， we learn that ＿＿＿＿＿＿＿＿.

Scientists are trying to make the deserts into good land again．They want to bring water to the deserts，so people can live and grow food．They are learning a lot about the deserts．But more and more of the earth is becoming desert all the time．Scientists may not be able to change the desert in time．
Why is more and more land becoming desert？Scientists think that people make deserts．People are doing bad things to the earth．
Some places on the earth don’t get much rain． But they still don’t become deserts． This is because some green plants are growing there． Small green plants and grass are very important to dry places． Plants don’t let the sun make the earth even drier． Plants do not let the wind blow the dirt away． When a bit of rain falls， the plants hold the water． Without plants， the land can become desert more easily．
【小题1】Deserts ＿＿＿＿＿＿＿＿ ．

What would you do if you were lost in the dark forest at night? The first sensible lesson is that you shouldn’t bother trying to find your way in the dark at all, but just stay where you are until dawn. Because then you won’t trip over things? No, mainly because you’ll have an idea of direction. The sun rises in the east. But you will be amazed at how many people forget they know that. Apparently, the area underneath a holly bush provides a good makeshift shelter — they are thick, and evergreen. The next thing to do — or rather not to do — is panic, for the obvious reason that unless there is someone there to hear you scream, it will get you nowhere. Just try to think of nice, happy things.

There is always a point in films when a person who is lost in the desert or the snow, dehydrated (脱水的) and exhausted, comes across a set of their own footprints and realizes they have just walked in a huge, round circle. It is wrong to owe it to the unequal strengths or different lengths of your legs. Experiments prove that, without the sun or the moon (or landmarks) as a fixed guide, lots of small errors add up over time so the brain can’t correctly identify the “straight ahead” direction. To just get out of somewhere, pick a spot on the horizon and just head for it.

There are several ways to find directions in the dark, and by far the best is to establish north using the stars. Most people can identify the Plough, which is part of Ursa Major. It looks a lot like a saucepan. The Plough rotates（旋转）through the sky, but let’s imagine the saucepan lying horizontally (水平地), with its handle on the left. You need to trace a line from the star at the right-hand base of the pan, through the star at the right-hand rim (边沿), and follow it upwards; the north star is roughly five times the distance between those two “pointer” stars. Then drop a vertical line from the North Star to the horizon and that’s north.

“Tonight is very cloudy and I can’t see the Plough.” Maybe luckily, it is quite windy. Keep in mind that almost all of our weather comes from a south-westerly direction. (This only works if you are in the British Isles). To find the direction, you can throw light bits of dried-out grass in the air and see which way they blow; or, if there are clouds and patches of clear sky, see which way they blow across the stars. You can also get an idea of direction from leggy plants. If they look as if they have been blown over, they will probably be pointing north-east. If they are simply leaning in one direction as they grow, there’s a good chance that is south (they will be reaching towards the sun). The last thing to do is to judge your direction and off you go.

What might be the best title of the passage?

A. How to survive in the forest

B. How to protect yourself in the forest

C. How to direct your way out of the wild

D. What to do if you are lost

Which of the following pictures matches the description of the position of the north star?

Why will people often walk in a circle if they are lost in the desert or the snow?

A. Because without anything to refer to for directions, the brain will be confused by errors.

B. Because one of the legs is longer and stronger than the other.

C. Because the desert or the snow usually covers a large area for people to get across.

D. Because people usually feel dehydrated and exhausted in the desert or the snow.

If you were lost in Taklimakan Desert in China, _________ would NOT be dependable for you to identify the directions.

A. the sun           B. the North Star        C. wind         D. the moon

In the 19^th century, Americans from the eastern states moved out west to settle in the rich new lands along the Pacific Coast. The most difficult part of their trip was crossing “the Great American Desert” in the western part of the United States by horse and wagon.
The western desert can be very dangerous. There is little water and there are few trees. But the desert also has scenery of great beauty. Tall towers of red and yellow stone rise sharply from the flat, sandy valley floor. The scene has been photographed many times and appears in movies and on TV.
In Arizona, man-made dams across the Colorado River have made two large lakes in the middle of the dry desert country. At Lake Powell, the red stone arch of Rainbow Bridge rises high above the blue lake.
There are few roads. Many areas of Lake Powell’s shore can only be reached by boat or on foot. But hikers in this empty desert land sometimes find very old native American pictures, painted on the rocks.
In Death Valley, California, the summer temperature rises to 130°F—165°F. There is less than inches of rain each year. Death Valley is the lowest place in America---925 metres below sea level. In the 1800s, many travelers died when they tried to cross this waterless valley in the terrible heat.
Although the desert is dry and seems empty, there is plenty of life if you look closely. Snakes and rats have learned how to live in the desert heat. They live underground and come out at night, when it is cool. Plants such as cacti need very little water. When it does rain in the desert (sometimes only once or twice a year), plants grow quickly, and flowers open in a single day. For a short time, the desert is covered with brilliant (very bright) colours.
【小题1】In the 19^th century, Americans moved from east to west because they            .

Flying over a desert in an airplane, two scientists looked down with trained eyes at trees and bushes. After an hour's flight one of the scientists wrote in his notebook, "Look here for probable metal." Walking across hilly ground, four scientists reported, "This ground should be searched for metals." From an airplane over a hilly wasteland a scientist sent back by radio one word "Uranium".

    None of the scientists had X-ray eyes: they had no magic powers for looking down below the earth's surface. They were merely putting to use one of the newest methods of locating minerals in the ground -- using trees and plants as signs that certain minerals may lie under the ground on which the trees and plants are growing.

    This newest method of searching for minerals is based on the fact that minerals deep in the earth may affect the kind of bushes and trees that grow on the surface.

    At Watson Bar Creek, a mineral search group gathered bags of tree seeds. Boxes were filled with small branches from the trees. Roots were dug and put into boxes. Each bag and box was carefully marked. In a scientific laboratory the parts of the forest trees were burned to ashes andtested. Each small part was examined to learn whether there were minerals in it.

    Study of the roots, branches and seeds showed no silver. But there were small amount of gold in the roots and a little less gold in the branches and seeds. The seeds growing nearest to the tree trunk had more gold than those growing on the ends of the branches.

    If the trees indicated that there was no gold in the ground, the scientists wouldn't spare money to pay for digging into the ground.

Scientists were flying over a desert or a hilly wasteland or a mountain region to ________.

A. train their eyes B. study the trees   C. look for gold         D. search for minerals

The study of trees, branches and roots indicated that __________.

A. there were larger amounts of gold in the branches far from the tree trunk than in the seeds

B. there were smaller amounts of gold in the tree roots deep in the ground than in the branches

C. there were larger amounts of gold in the seeds growing closer to the tree trunk than in the seeds farther from it

D. there were larger amounts of gold in the branches than in the leaves on the ends of the branches

Which of the following is NOT mentioned as part of a tree that can help the searchers?

A. Leaves.          B. Roots.            C. Branches.           D. Seeds.

Which of the following might be the best title for this passage?

A. Scientists searching for treasure with special equipment.

  B. New methods of doing geological study.

C. Gold could be found in trees and plants.

D. A new method of searching for minerals.