Itwasoncethoughtthat的精選

問題詳情：Itwasoncethoughtthatairpollutionaffectedonlytheareaimmediatelyaroundlargecitieswithfactoriesand/orheavyautomobiletraffic.Today,weknowthatalthoughthesearetheareaswiththeworstairpollution,thepro...