Peopleandthesourcesofairpollutionarefoundinthesamep...
问题详情: Peopleandthesourcesofairpollutionarefoundinthesameplaces.Thismeansthatcitieswithlargepopulationshavethebiggestproblemofdirtyair.Airpollutioniscausedbymanydifferentthings.Amajorsourceof...