A white chalk chalks white on a black blackboard.一根白色的粉笔在黑色的黑板上写白字.His steed was by chalks the best.他的马是最好的.The prisoner has walked his chalks , and is off to London.那囚犯逃走了, 逃到伦敦去了....drawing a small picture with coloure...
化石燃料（如煤和石油）属于有限资源。The fossil fuels (coal and oil) are finite resources.发电站烧的煤产自鲁尔地区。The power stations burn coal from the Ruhr region.酸雨并非简单地由烧煤造成。Acid rain is not straightforwardly attributable to the burning of coal....