Four friends write a description of pitch.
Jessica: Pitch is how high or low a sound is. The pitch depends on vibrations. High pitch sounds have low amounts of vibrations.
Rachael: Pitch describes how high or low a sound is. Sounds are caused by vibrations. The more vibrations, the higher the pitch.
Harvey: Pitch is caused by vibrations. The more vibrations, the lower the pitch of the sound.
Derek: Pitch is how high or low a sound is. All sounds have mostly the same pitch.

Who has the best description of pitch? (2 points)

a
Jessica

b
Rachel

c
Derek