19.21.Water is called liquid gold because it'svery precious and water resources are limited. 22.There'splenty of salty water in the sea,but we can neither drink nor take a shower with it. 23.Floods are powerful and harmful and they can causehuge damage in economy. 24.People whosuffer from an earthquake or a flood may have nowhere to live. 25.People donate (捐贈).money,food,water and medicine tothe homeless through the Red Cross.