Forseveralbillionyearsafterthe“BigBang”,theearthwassti...
问题详情： Forseveralbillionyearsafterthe“BigBang”,theearthwasstilljustacloudofdust.Whatitwasto______(36)wasuncertainuntilbetween4.5and3.8billionyearsagowhenthedustsettledintoasolidglobe.Theearthbeca...