单词：bacteriological filtration
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Beijing will launch a pilot program to equip schools and kindergartens with air filtration devices. Smog has been a significant issue in the Chinese capital this winter. I was coughing just now, I always wear mask, from school to home. The air is cho
发表于:2018-12-02 / 阅读(188) / 评论(0)
2017CRI中国国际广播电台
2017CRI中国国际广播电台
By Tabinda Naeem Washington, D.C. 21 May 2007 Two years ago, the National Academy of Engineering established the Grainger Challenge Prize for Sustainability. This $1 million award was designed to challenge the world's scientists to develop a practica
发表于:2019-02-03 / 阅读(211) / 评论(0)
2007年VOA标准英语（五月）
2007年VOA标准英语（五月）