- And oxygen filled the air.
从此 空气中出现了氧 - The earth's water cycle is a process of constant renewal.
地球的水循环是一个持续更新的过程 - Waterfalls, watervapor,
瀑布 水蒸气 - Clouds, rain, springs,
云 雨 溪流 - Rivers, seas, oceans, glaciers.
河 海 洋 冰川 - The cycle is never broken.
这一循环从未被打破 - There's always the same quantity of water on earth.
地球上的水含量是恒定的