The air different gases together.A.consist of, mixingB.is made up of, mixedC.consisting of, mixedD.makes up, mixing 题目和参考答案——青夏教育精英家教网—

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　　Soil conservation(保护)efforts protect soil from wind and water that can blow or wash it away．[1]_________ One important form of soil conservation is the use of windbreaks．Windbreaks stop the wind from blowing soil away．They also keep the wind from destroying or damaging crops．Windbreaks are barriers formed by trees and other plants with many leaves．[2]_________ Windbreaks are effective when a wall of trees and other plants blocks the wind．The windbreaks should also limit violent motions of the wind to those areas closest to the windbreak．

　　[3]_________ If the wall of trees and plants stops wind completely, then violent air motions will take place close to the ground．These motions cause the soil to lift up into the air where it will be blown away．[4]_________ An easy rule to remember is that windbreaks can protect areas up to ten times the height of the tallest trees in the windbreak．There should be at least two lines in each windbreak．One line should be large trees．The second line, right next to it, can be formed from shorter trees and other plants with leaves．Windbreaks not only protect land and crops from the wind．They can also provide wood products．[5]_________

a．Windbreaks seem to work best when they allow a little wind to pass through．

b．Good soil produces food crops for both humans and animals．

c．For the long term, trees will be planted throughout the area to act as windbreaks which will provide adequate protection．

d．Farmers plant windbreaks in lines around their fields．They are very important when grains such as wheat are grown．

e．Plantations are also sometimes known as “man made forests” or “tree farms”．Environmental Plantations may be established for watershed or soil protection．These are established for erosion control, landslide stabilization and windbreaks reduce carbon di oxide and increase oxygen levels in atmosphere．

f．These include wood for fuel and longer pieces for making fences．Locally grown trees and plants are best for windbreaks．

g．For this reason, a windbreak is best if it has only 60 to 80 per cent of the trees and plants needed to make a solid line．

There are various reasons why cancers appear to be on the increase. For one thing, though their sufferers are to be found in all age groups, cancers are particularly likely to attack persons in their middle and advanced years. Naturally, since people live longer these years, there are more cancer sufferers than before. Again, with better methods of diagnosis (诊断), doctors can more easily recog??nize cancerous growths that would formerly have passed unnoticed or that would have been wrongly di??agnosed. It is also believed that certain habits and conditions of modem living, including heavy smok??ing and the pollution of the air, may leave people living in more cancer-causing conditions than before.

We all look forward to the day when a simple medical test can find cancer while it is still small. Researchers around the world are working on such a test. Most of their work deals with the examina??tion of the blood.

Researchers in Boston have found something in the blood of cancer patients that does not appear in healthy persons. The test showed which persons had cancer and which did not. It was correct more than 90 percent of the time.

The researchers believe the test may be able to show cancer very clearly in its development. Cancers discovered early usually can be treated successfully.

The test examines very small bits of fat in the blood called lipids (脂质). Cancers seem to change lipids although doctors do not know why. The test showed differences between the lipids of the persons with cancer and the lipids of those without cancer.

The researchers say the new test could be a step to develop a simple way to check patients for cancer before the disease shows on an X-ray.

1. Who will fail cancer from the study of the researchers?

A. The young. B. The middle age and the older.

C. The man. D. The woman.

2. The underlined words "such a test" refer to________.

A. the test that shows which persons have cancer and which don’t .

B. the test that may be able to show cancer very early in its development,.

C. a simple medical test that cannot find cancer when it is -small

D. a new test that could be a step to develop a difficult way

3. Which of the following statements is true according to the passage?

A. Cancers have much to do with something in patients’ blood.

B. People living in better conditions are most likely to be attacked by cancer.

C.X-raying is the best way to determined whether a person has cancer or not.

D. Cancers have nothing to do with a person’s habits and living conditions.

4. What would be the best title for the passage?

A. A simple way to cancer B. Cancers can be cured

C. How to find cancer D. Early discovery of cancer

There are various reasons why cancers appear to be on the increase. For one thing, though their sufferers are to be found in all age groups, cancers are particularly likely to attack persons in their middle and advanced years. Naturally, since people live longer these years, there are more cancer sufferers than before. Again, with better methods of diagnosis (诊断), doctors can more easily recog??nize cancerous growths that would formerly have passed unnoticed or that would have been wrongly di??agnosed. It is also believed that certain habits and conditions of modem living, including heavy smok??ing and the pollution of the air, may leave people living in more cancer-causing conditions than before.