（2021·昆明摸底測试）Washington is home to lots of trees. It is the Evergreen State， with lots of fireplaces and wood？_______......

在云南省绿春县的有些村庄,由砍柴造成的森林破坏是造成环境退化的主要原因.在黑河流域的上游,不断加剧的水土流失和河床抬升对下......

The relationship between out-migration of labor in the Qinling mountain area and households＇ firewood consumption is expl......