Many years ago it was taught that plants and animals were composed of different materials: plants, of a chemical substance of three elements,- carbon, hydrogen, and oxygen; animals of one of four elements, nitrogen being added to the other three.
许多年前，人们就知道植物和动物是由不同的物质组成的:植物是由三种元素组成的化学物质——碳、氢和氧;四种元素之一的动物，氮被添加到其他三种元素中。
标签
Plants
Animals
Composed
Elements