45.The source of Energy A summary of the physical and chemical nature of life must begin, not on the Earth, but in the Sun; in fact, at the Suns very center. It is here that is to be found the source of the energy that the Sun constantly pours out i

发表于:2018-11-28 / 阅读(348) / 评论(0) 分类 新概念优美背诵短文50篇

Lightning Helps Fertilize The Soil Our bodies need protein, and proteins contain nitrogen. The air we breathe has plenty of nitrogen to satisfy our needs. Butthat nitrogen is not available to us directly from the air. The only way we can get nitrogen

发表于:2018-12-31 / 阅读(56) / 评论(0) 分类 英语听力文摘 English Digest

The Time Before Fire What is fire anyway? Well, fire is rapid oxidization . Its the energy released when oxygen atoms start combining with carbon and hydrogen atoms. Exactly, so without oxygen in the air, nothing burns. You mean there was a time befo

发表于:2019-01-26 / 阅读(60) / 评论(0) 分类 英语听力文摘 English Digest