spentadj.失效的；精疲力竭的动词spend的过去式和过去分词spent meal脱脂粉spent acid废酸spent fuel烧过的核燃料spent oxide废氧化物,失效的海绵铁spent acids乏酸spent force过时的人spent steam废汽spent riser待生催化剂提升管spent water废水spent baths废液

1. He does not know how to make use of this waste gas.
   他不知如何利用这种废气。
2. Cars pollute the air in the form of waste gas.
   汽车以废气的形式污染空气。