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 （捐赠）．money，food，water and medicine tothe homeless through the Red Cross．
