prep19

清凉凉

Google 原句
                

Industrialization and modern
            insect
            control
            have, according to this story,

improved the quality of life around the globe, but they
            have also added some 100,000 chemical compounds that, some scientists worry, could affect the health of people and wildlife. The story says that these persistent organic pollutants, known as POP's,have gone virtually unregulated since they were developed more than 50 yearsago,

第一个they指methods，第二个指pollutants