SinceJanuary2013,manycitiesinChinahaveseenalotoffoggyda...
問題詳情：SinceJanuary2013,manycitiesinChinahaveseenalotoffoggydays.InBeijing,onlyfivedaysinJanuarywerefreeofsmog(霧霾).What’sthedifferencebetweenfogandsmog?Accordingtoscientists,fogismadeupoftiny(微小...