health,surroundedby,smog,anythingbut,gases,impurities,absorb,poisonous,tryhard,blackedout 　　Weallknowthatcleanairisimportanttogoodhealth.Whereveryougoandwhateveryoudo,youarealwayssurroundedbyaseaofgasesthatwecallair.Ifthereareimpuritiesintheair,theymaybeabsorbedbyourbodiesandmakeusill.Weneedcleanair,butunfortunately,airpollutionisgloballypresent,especiallyincities. 　　Manylargecitiesareanythingbutpollution-free.Ourcitieshavemanyfactories,whichweneedtomakefood,clothingandotherthings.Everyyearthesefactoriespourmillionsuponmillionsoftonsofsmogintoair.Powerplantsandhousesthatburncoaladdgreatlytoairpollution.Besides,therearemorecarsincitiesnow.Onceoutonthestreets,theywilltakeinfreshairandreplaceitwithpoisonousgases. 　　Ourcountryistryinghardtopreventandcontrolairpollution.Aslongaseverycitizenalsorealizesitsimportanceandmakesjoinefforts,thedaywillcomesoonwhenpeoplewilltakeinonlycleanair.Then,thesunlightwillnolongerbeblackenedoutbysmokeandsoot.