In1620,abouthalftheUSAwascoveredbyforests.Todaythefor...
問題詳情： In1620,abouthalftheUSAwascoveredbyforests.Todaytheforestshavealmostgone.Alotofgoodlandhasgonewiththem,leavingonlysand.Chinadoesn'twanttocopytheUSA'sexample.We'replantingmoreandmoretrees...