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.

转炉烟气净化方式有哪些？