VOA慢速英语:Washington’s Environmental Film Festival Celebrates its 18th Year

例句：declining soil fertility
      正在下降的土壤肥力

      A green manure is a crop grown mainly to improve soil fertility.
      种植绿肥作物主要是为使土壤更加肥沃。

2.shortage n.缺乏,不足

例句：There is a shortage of trained nurses.
      受过正规训练的护士十分缺乏。

3.animate v.绘制(卡通影片)

4.define vt.定义,解释,下定义,限定,规定

例句：Define a word by capitalizing it and putting it in quotes.
      强调一个合同术语可以这样做:加上双引号并将其开头的字母大写。