根据短文内容(英文),完成下面的问题
Lifetodayismucheasierthanitwashundredsofyearsago,butithasmanynewproblems.Onecfthebiggestproblems.
Themorepeople,themorepollution.Manyyearsago,theproblemswasnotsoseriousbeacusetherewerenotsomanypeople.Whenpeopleusedupthelandortheriverwasdirtyinoneplace,theymovedtoanotherplace..Humansarenowpollutingthewholeworld.
Pollutioncomesinmanyways,Weseeit,drinkitandevenhearit.Airpollutionisstillthemostserious.It'sbadforalllivingthingsintheworld.ThepollutionofSO₂isnowthemostdangerousproblemofairpollution.Itcomesfromheavytransportation.Waterpollutionkillsourfishandmakesourdrinkingwaterdirty.Noisepollutionmakesusbecomeangrymoreeasily.
Manycountriesaremakingrulestofightagainstpollution.Peoplemustn'tburncoalinthehousesandfactoriesinthecityorbringdirtysmokeintotheair,
1、Waysofpollution(atleast3)
2、Thecauseofpollution
3、Waystofightagainsthundredsofyearsago
4、Waystofightagainstpollutionnow