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A girl is playing a guitar and a boy is playing the drums.
The boy's guitar makes a higher sound than the girl's drum. Which reason BEST describes why this might happen?
a. the drum has a higher pitch than the guitar
b. the drum makes a louder sound than the guitar
c. the guitar's parts vibrate, but the guitar's parts do not
d. the guitar's parts vibrate more quickly than the drum's parts
What is d. the guitar's parts vibrate more quickly than the drum's parts