Industrialization and modern methods of insect control have improved the standard of living around the globe while at the same time they have introduced some 100,000 dangerous chemical pollutants, having gone virtually unregulated since they were developed more than 50 years ago.
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Awhile at the same time they have introduced some 100,000 dangerous chemical pollutants, having
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Bwhile at the same time introducing some 100,000 dangerous chemical pollutants that have
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Cwhile they have introduced some 100,000 dangerous chemical pollutants at the same time, and have
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Dbut introducing some 100,000 dangerous chemical pollutants at the same time that have
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Ebut at the same time introducing some 100,000 dangerous chemical pollutants, having
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正确答案: B