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 re stored can provide more information than can one that has been restored.
E．(E) An eighteenth-century instrument cannot serve as a source of new information about eighteenth-century instrument-making techniques once it can be played.
。直面型，乳前牙反
反可能与下列哪些因素有关（）.