[单项选择] Not many of the elements occur in nature as pure substances, lying around waiting for someone to pick them up. A few do, and it is not surprising that these were known and collected for various uses in societies around the globe as far back as several thousand years B. C. Sulfur is one of those elements. It was known to burn with smelly results and have an odd appearance. Its use was probably confined to religious ceremonies. Carbon was also known since antiquity, because the charred (烧焦的) bones of animals and portions of partially burned trees consist largely of carbon in the form of charcoal. Although we don’’t know all the uses primitive peoples made of charcoal, we do know that it was the key to releasing many other elements from their chemical combination in rocks. For example, if a copper-containing rock was heated in a hot fire with charcoal present, the carbon in the charcoal would combine with the other elements in the rock, leaving free metallic copper. In ways like this
A. Not many elements occur in nature as pure substances, therefore ancient people wouldn’’t pick them up.
B. Ancient people found copper, iron, lead, tin and zinc very useful, although they did not consider these to be elements.
C. Ancient people discovered elements, found them free or lying around in their natural form and put them to use.
D. Sulfur and carbon have been used by mankind for thousands of years, but not much has been known about them.