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当你打开水龙头的时候,清洁的自来水就会从中流出。那么,江河湖泊中的水究竟是怎么变成饮用水的呢?我们用了这些水之后,又会发生什么变化呢?
When you turn on the tap, clean tap water will flow from it. So how did the water in rivers and lakes turn into drinking water? After we used this water, what changes will happen?