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BR>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.
36、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.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