49. According to the passage, which of the following statements is true?
(A)The musical notation for pitch was invented after the 10th century.
(B)How the representation of the bass clef has been evolved is detailed in the passage.
(C)In the past, the deficiency of printing limited the precision of how clefs on music staves were duplicated.
(D)With the position on a music staff unchanged, a note on the tenor clef has a higher pitch than that on the alto clef.