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  3. Air pollution is one of the most pervasive environmental problems because atmospheric currents can carry contaminated air to eve

Air pollution is one of the most pervasive environmental problems because atmospheric currents can carry contaminated air to eve

admin2010-08-21  51
问题     Air pollution is one of the most pervasive environmental problems because
atmospheric currents can carry contaminated air to every part of the globe.
Most air pollution comes, from automobile emissions and from power plants
what burn coal and oil to produce energy for industrial and consumer use.          【S1】______
Carbon dioxide and other harmful gases releasing into the air from these           【S2】______
sources adversely effect weather patterns and the health of people, animals and    【S3】______
plants.
    Industrialized nations produce most of the world’s air pollution. For          【S4】______
example, because the United States is home to just 5 percent of the world’s
population, the country generates 22 percent of human-made carbon dioxide          【S5】______
emissions or 19 percent of all greenhouse gases such as carbon dioxide and         【S6】______
methane. These emissions harm the environment by leading acid rain and
global warming, and by depleting (使衰竭) the protective ozone layer which         【S7】______
surround the earth.
    Acid rain, a serious threat around the world, occurs when sulfur dioxide
and nitrogen oxide emissions from automobiles and fossil-fuel burning power        【S8】______
plants to fall back to Earth as acidic precipitation. Acid rain has contaminated
many lakes in Canada and the northeast United States and has been
documented even in the non-industrial state of Hawaii. In the United               【S9】______
Kingdom, 57 percent of all trees are severely defoliated (使落叶) owe to           【S10】______
corrosive fallout, and production of food crops has been declined in many parts
of the world. Acid rain has eroded the surfaces of great art and architectural
treasures, including the ancient sculptures of Rome and the Sphinx in Egypt.
【S4】
选项
答案because→although
解析 从上下文看，本句的意思是“美国的人口只占世界人口的5%，却制造出22%的人造二氧化碳……”，前一分句用了“just”一词，和后面形成了强烈的对比，因此这两个分句之间是转折关系，而不是因果关系，前一分句前应该用although引导。
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