Oxygen 来自幽默学英语网http://www.linkstom.cn/humor/
The science teacher was explaining to the class. "Oxygen is necessary to all life. Without it there'd be no life at all. Now just think -- it was only discovered about 100 years ago."
Jenny raised her hand and asked, "If that's true, what did people do before it was discovered?"

氧气
自然科学老师在课堂上讲到：“氧气对任何生命都是必不可少的。如果没有氧气，地球上将不会有任何生命存在。大家想想--氧气的发现只有100多年。”
詹妮举起手问：“假如这是真的话，那么在氧气没有被发现以前人类是怎么活的？”