Passage2Youmayhaveheardthesaying“TheYangtzeRiverChina'smotherriver.”Itisalmost6400kilometerslong.Astheworld’sthird-longestriver,itcoversone-fifthoflandarea.TheYangtzeRiverEconomicZone(长江经济带)coverselevenprovincesandcities,makingupaboutfortypercentofChina’stotalpopulationandGDP.OnDecember26,ChinapassedtheYangtzeRiverProtectionLaw,whichcameintoforceonMarch1,2021.ItisthefirstlawtoprotectawaterwayinChina.Themotherriverisingreatneedofprotectionbecausesomethingiswrongwithit.Forexample,becauseofoverfishingandwaterpollution,theriver’sChinesepaddlefishhasdiedoutthere.There’salsodesertifiedlandandsoilpollutionneartheriver.Accordingtothelaw,fishingwillnotbeallowedinalloftheYangtze'snaturalwaterways,includingitsmajortributaries(支流)andlakes.Thosewhoarecaughtfishingwillbefined(罚款)50000to500000yuan.Diggingsandwillbestrictlylimited(限制)intheriver.Manycompaniesarediggingsandalongtheriver.However,thishasledtolowerwaterlevelsontheriver,whichhascausedtheriver’swatertodecline.Companiesandfactoriesalongtheriverwillneedtofocusongreendevelopment.Iftheiractivitiesdoharmtothewaterways,theywillbemovedaway,thelawsays.9.Whatdoestheunderlinedword“decline”inParagraph5mean?