论文部分内容阅读
Do You Know Nearly 97 percent of all the world’s water is salty or otherwise undrinkable. Another 2 percent is locked in ice caps and glaciers(冰河).That leaves 1 percent for all our needs.Water
Do You Know Nearly 97 percent of all the world’s water is salty or otherwise undrinkable. Another 2 percent is locked in ice caps and glaciers. Hat leaves 1 percent for all our needs. Water