一道逻辑单题！求解答！！

Playing eighteenth-century music on the instruments of that period provides valuable information about how the music originally sounded. Eighteenth-century instruments cannot be played without being restored， however， and restoring such an instrument destroys all of the information that researchers could obtain from it about eighteenth-century instrument-making techniques.
　　If the statements above are true， which of the following must be true on the basis of them？
　　（A） Eighteenth-century instruments cannot be used to provide information about the original techniques used in playing such instruments if they have been restored.
　　（B） Eighteenth-century instruments that have been restored can provide information only about how eighteenth-century music originally sounded
　　（C） Eighteenth-century instruments are the only source of information about the instrument-making techniques of that period.
　　（D） An eighteenth-century instrument that has not been restored can provide more information than can one that has been restored.
　　（E） An eighteenth-century instrument cannot serve as a source of new information about eighteenth-century instrument-making techniques once it can be played


我知道E是对的 为什么C不对 阿！！