The air surrounding us is important to everyone.Without air, we could not exist.Everyone understands that.But air is necessary in many other ways――ways that are not always so obvious or widely known.

　　我们周围的空气对大家都很重要。没有空气，我们就无法生存。每个人都明白这一点。但是在很多其他方面――那些不大明显或不大为人所知的方面，空气也是必不可少的。