四大洋: the Atlantic, the Pacific, the Indian, the Arctic 表示分数的词: three quarters,two thirds,half 表示水域的词: ocean,lake,pond,river, stream,spring 水的三种形态: solid,liquid,gas 自然界中的水: vapor, droplet, fog, dew, frost, cloud, shower,drizzle, sleet, hail depend on 取决于;依靠 run out of 用完 get rid of摆脱;除去 nothing but 只有;只不过 believe it or not 信不信由你 a variety of种种;各种各样的 as 引导的时间状语从句，例如: As rain falls and snow melts, waterflows downhill. whenever引导的时间状语从句，例如: Your body loses waterwhenever you sweat or go to the bathroom. “that's why”句型，例如: That's why people check the weatherreport before deciding what clothes to wear and how to spend theday.