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  3. One reaction to all the concern about tropical deforestation is a blank stare that asks the question , "Since I don’ t live in t

One reaction to all the concern about tropical deforestation is a blank stare that asks the question , "Since I don’ t live in t

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问题     One reaction to all the concern about tropical deforestation is a blank stare that asks the question , "Since I don’ t live in the tropics, what does it have to do with me? " The answer is that your way of life, wherever you live in the world, is tied to the tropics in many ways. If you live in a house, wash your hair, eat fruit and vegetables, drink soda, or drive a car, you can be certain that you are affected by the loss of tropical forests. Biologically, we are losing the richest regions on earth when, each minute, a piece of tropical forest the size of ten city blocks vanishes. As many as five million species of plants, animals and insects, 40 to 50 percent of all living things, live there, and are being irrevocably lost faster than they can be found and described. Their loss is incalculable.
    Take medicine, for example. Fewer than one percent of tropical forest plants have been examined for their chemical compounds. Nonetheless, scientists have integrated a wealth of important plants into our everyday lives. The West African calabar bean is used to treat glaucoma, while the sankerfoot plant of India yields reserpine, essential for treating hypertension. A West African vine provides the basis for strophanthus, a heart medicine. Quinine, an alkaloid derived from boiling the bark of the cinchona tree, is used to prevent and treat malaria. Derivatives from the rosy periwinkle offer a 99 percent chance of remission for victims of lymphocytic leukemia, as well as a 59 percent chance of recovery from Hodgkin’s disease. In fact, of the 3 000 plant species in the world known to contain anti-cancer properties, 2 100 are from the tropical rain forest. Then there is rubber. For many uses, only natural rubber from trees will do, synthetics are not good e-nough. Today, over half of the world’ s commercial rubber is produced in Malaysia and Indonesia, while the Amazon’ s rubber industry produces much of the world’ s four million tons. Adding ammonia to rubber produces latex which is used for surgical gloves, balloons, adhesives, and foam rubber. Latex, plus a weak mixture of acid results in sheet rubber used for footwear and many sporting goods. Literally thousands of tropical plants are valuable for their industrial uses. Many provide fiber and canes for furniture, soundproofing and insulation. Palm oil, a product of the tropics, brings to your table margarine, cooking oil, bakery products, and candles. Palm nut oil, from the seed kernel inside the fruit, is found in soap, candles, and mayonnaise. The sap from Amazonian copaiba trees, poured straight into a fuel tank, can power a truck. At present, 20 percent of Brazil’ s diesel fuel comes from this tree. An expanded use of this might reduce our dependency on irreplaceable fossil fuels.
    Many scientists assert that deforestation contributes to the greenhouse effect, the heating of the earth from increased carbon dioxide in the atmosphere. As we destroy forests, we lose their a-bility to convert carbon dioxide into oxygen. Carbon dioxide levels could double within the next half-century, warming the earth by as much as 4.5 degrees. The result? A partial melt-down of the polar ice caps, raising sea levels as much as 24 feet. A rise of 15 feet would threaten anyone living within 35 miles of the coast. Farfetched? Perhaps, but scientists warn that by the time we realize the severe effects of tropical deforestation, it will be 20 years too late. Can tropical deforestation affect our everyday lives? We only have to look at the catalogued tropical forests and the abundance of wondrous products from which we benefit every day to know the answer. After all, the next discovery could be a cure for cancer or the common cold, or the answer to feeding the hungry, or fuelling our world for centuries to come.
Which statement best expresses the main idea of the article?
选项 A、Many different kinds of medicine come from tropical forests.
B、Virtually all of the world’ s rain forest has already been destroyed.
C、Tropical forests are disappearing at an alarming rate.
D、Tropical deforestation affects people in all parts of the globe.
答案D
解析 综观全文，先是强调热带雨林对人类的价值，再讲热带雨林的减少对人类生活可能产生的影响。因此D项为正确答案。
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