![Morethanhalfoftheworld’spopulationlivesincities.Traffic...]( "Morethanhalfoftheworld’spopulationlivesincities.Traffic...")
- 问题详情：Morethanhalfoftheworld’spopulationlivesincities.Trafficandpollutionarebecomingbigproblemsinbigcitiesallovertheworld.IncitieslikeMexicoCity,ShanghaiorCairothequalityoftheairisgettingworseeveryday.IntheUnitedStates,peoplespendmoretimesittingin...
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