学位英语

第三篇

Population Densities The average population density of the world is 47 persons per square mile. Continental densities range from no permanent inhabitants in Antarctica to 211 per square mile in Europe. In the western hemisphere, population densities range from about 4 per square mile in Canada to 675 per square mile in Puerto Rico. I n Europe the range is from 4 per square mile in Iceland to 831 per square mile I n the Netherlands. Within countries there are wide variations of population dens ities. For example, in Egypt, the average is 55 persons per square mile, but 1,3 00 person inhabit each square mile in settled portions where the land is arable. High population densities generally occur in regions of developed industri alization, such as the Netherlands, Belgium, and Great Britain, or where lands a re intensively used for agriculture, as in Puerto Rico and Java. Low average population densities are characteristic of most underdeveloped countries. Low density of population is generally associated with a relatively low percentage of cultivated land. This generally results from poor quality land s. It may also be due to natural obstacles to cultivation, such as deserts, moun tains, or malaria (疟疾)-infested jungles; to land uses othe r than cultivation, as pasture and forested sand; to primitive methods that limit cultivation; to so cial obstacles; and to land ownership systems which keep land out of production. More ***nomically advanced countries of low population density have, as a rule, large proportions of their populations living in urban areas. Their rural population densities are usually very low. Poorly developed countries of corresp ondingly low generally population density, on the other hand, often have a conce ntration of rural population living on arable land, which is as great as the rur al concentration found in the most densely populated industrial countries.

31、Along the banks of the Nile, we may expect to find____

A.1300 persons.B. Few inhabitants.

B.few inhabitants.

C.pyramids.

D.many settlements.

32、(同31题)The most densely populated continent is____

A.Asia.

B.Africa.

C.Europe.

D.North America.

33、(同31题)There are no permanent inhabitants in Antarctica because____

A.it is too hot.

B.It is too cold.

C.there is no transportation.

D.it has only recently been discovered.

34、(同31题)In highly industrialized communities, we may expect_____

A.large rural areas.

B.urban development.

C.epidemics.D. Arable land.

D.arable land.

35、(同31题)Puerto Rico is a land of____

A.heavy industrialization.

B.poverty.

C.intense agriculture.

D.large cities.

第四篇

Suntans and Skin Cancer Between now (June) and Labor Day, millions of Americans will offer up thei r bodies to the sun’s rays. A tan indicates health and beauty, and most sun wors hippers will sacrifice a lot to achieve it ? Including themselves. With each hou r, the sun’s ultraviolet (紫外线) radiation produces irrever sible (不可逆的) dam age, hastening the development of unsightly wrinkles. And with each year on the beach or rooftop, the sunbather increases his risk of getting skin cancer. Skin cancer is by far the most common form of cancer. An estimated 400,000 new cases will be detected this year in the United States, and almost all of th em can be blamed on overexposure to the sun. Fortunately, most of these cancers are highly curable. But they can be disfiguring and take time to treat. For that reason, sun worshippers should treat deity with a good deal of awe ( 敬畏). Sunburn, of course, is the initial hazard posed by UV radiation. Prolonged exposure to UV, however, interferes with the production of collagen fibers in t he dermis, causing the skin to lose elasticity and creating premature wrinkles. Further deterioration of the dermis deprives the epidermis of nutrition and caus es it to b***me thin and dry. Cancer is UV’s final insult. Shortwave radiant energy, especially from the UV-B band, breaks the strands of DNA. Enzymes work constantly to rearrange the DNA into proper sequence, but with repeated UV exposure, the repair process may eventually break down. Then the mutant DNA may produce a colony of cancer cells. But skin cancer may be avoided with a good dose of common sense. People wi th fair skin and blue eyes who burn easily stand the highest risk. Special dange r spots are the parts of the body most constantly exposed to the sun, such as th e cheeks, nose, lower lip and the ears. People who have already developed precan cerous lesions or had one skin-cancer growth stand a greatly increased chance of developing others. Dermatologists r***mmend avoiding the sun when it is most in tense?between 11 a.m. and 3 p.m. Anyone who insists on sunbathing should use a g ood sun screen. These lotions and salves contain chemicals, such as para-aminobe nzoic acid, that block out the burning UV-B radiation while permitting the tanni ng rays to reach the skin.

36、According to the passage, overexposure to the sun may result in____

A.the wrinkles that cannot be seen.

B.The skin cancer.

C.all kinds of sacrifices.

D.healthful beauty.

37、(同36题)The word \!deity" in the s***nd paragraph refers to_____

A.something mysterious.

B.the skin cancer.

C.the sun.

D.overexposure to the sun.

38、(同36题)Which of the following comes first as a possible damage by UV radiation?____

A.Sunburn.

B.The loss of skin elasticity.

C.Dryness of epidermis.

D.The deterioration of dermis.

39、(同36题)Why does the repair process of the DNA may finally fail?____

A.Because shortwave radiant energy breaks the strands of the DNA.

B.Because the DNA may produce a colony of cancer cells.

C.Because enzymes work to rearrange the DNA into a new order.

D.Because the patient is exposed to UV from time to time.

40、(同36题)The last paragraph of the passage mainly discusses____

A.the treatment of the skin cancer.

B.the prevention of the skin cancer.

C.the parts of the body where cancer is most likely to develop.

D.the lotions that work best in fighting against the skin cancer.

第五篇

Smoking and Cancer Americans smoke six thousands million cigarettes every year (1970 figures). This is roughly the equivalent of 4195 cigarettes a year for every person in the country of 18 years of age or more. It is estimated that 51 % of American men s moke compared with 34 % of American women. Since 1939, numerous scientific studies have been conducted to determine whe ther smoking is a health hazard. The trend of the evidence has been consistent a nd indicates that there is a serious health risk. Research teams have conducted studies that show beyond all reasonable doubt that tobacco smoking, particularly cigarette smoking is associated with a shortened life expectancy. Cigarette smoking is believed by most research workers in this field to be a n important factor in the development of cancer of the lungs and cancer of the t hroat. Male cigarette smokers have a higher death rate from heart disease than O n-smoking males. Female smokers are thought to be less affected because they do not breathe in the smoke so deeply. The majority of physicians and researchers consider these relationships proved to their satisfaction and say, ’Give up smoking! If you don’t smoke, don’t start! ’ . It might be helpful to look at what tobacco-smoking actually does to the hum an body. Smoke is a mixture of gases, vaporized chemicals, minute particles of a sh, and other solids. There is also nicotine, which is a powerful poison, and bl ack tar. As the smoke is breathed in, all these components form deposits on the m

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