大学英语自学教程 上册 un08

[11:19.52]have begun to pay attention to air.
[11:21.40]也开始注意空气。
[11:23.29]We realize that air does not contain the same elements
[11:25.70]我们认识到，现在空气所含的元素
[11:28.12]that it contained years ago.
[11:29.84]和多年前不一样。
[11:31.57]Automobiles, airplanes, factories,and atomic explosions
[11:35.25]汽车、飞机、工厂以及核工业爆炸
[11:38.93]have added dust and waste gases to the atmosphere.
[11:41.36]往大气中增添了很多尘埃和废气。
[11:43.79]It is time to learn how to protect our atmosphere,
[11:46.08]现在该 是我们应该学会怎样保护我们的大气
[11:48.36]the roof over the world of man.
[11:50.33]人类世界的屋顶的时候了。