VOA慢速英语:Solar-Powered Pumps Aid African Farmers

例句：They are digging irrigation ditches.
       他们在挖灌溉渠。

2.rainfall n.降雨,降雨量

例句：The flood had been caused by uNPRecedented rainfall.
      洪水是由于前所未有的大量降雨造成的。

3.collectively ad.集体地;共同地

例句：We should not embezzle property that is collectively owned.
      集体的财物不能贪占。

4.surplus a.过剩的,剩余的

例句：They will close all surplus factories over the next six months.
      他们将在接下来的六个月关闭所有多余的工厂。

5.serving n.服务,招待,上菜,一份食物

例句：This is a serving dish that we mostly used for Thanksgiving.
      我们一般在感恩节用这个盘子。

6.economical a.节俭的,经济的,合算的

例句：She is economical with/in her use of salt when cooking.
      她烹饪时用盐很省。

      He is economical of his time.
      他节省时间。