填空题 For this study, investigators analyzed the component of air pollution known as fine particulate matter (PM2.5)—the tiny pieces of solid or liquid pollution _____ from motor vehicles, factories, power plants, fires, and smoking.(emit)无
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【正确答案】 1、emitted    
【答案解析】此题考查非谓语动词， 根据句型可知设空处表示被动的非谓语动词， 故用emit的过去分词形式emitted。