The modern world, however, has found more important uses for its diamonds than the making of jewellery. They have been put to work; (1)__________________________. It can cut or polish the hardest steel or grind its way through solid rock.Only a diamond is hard enough to cut another diamond, and it is not the big stones which are needed for the drills, saws and grinding wheels. (2)_________________________________.
Yet it is a strange fact that nature makes its hardest mineral from exactly the same substance as one of its softest. This soft mineral is graphite, which is very easily broken up and is used to make the “lead” in your pencil. The name “lead” should not really be used, (3)_______________________—just the same as a diamond.
本帖隐藏的内容需要回复才可以浏览
作者: susan.sui 时间: 2012-7-30 10:25
1. for diamond, it's hard to break through found in Nora.
2. only factories ******
3.because graphite consists of nothing but carbon作者: 杨飞飞儿 时间: 2012-7-30 13:31
