读等高线地形图，回答下列问题。
古语道：“人要实，火要虚。”此话的意思是说：做人必须脚踏实地，事业才能有成；燃烧木柴需要架空，燃烧才能更旺。从燃烧的条件看，“火要虚”的实质是
In his victory speech，______ before a huge crowd of his supporters，Obama declared that “change has come to America”．
