Question

1. what determines pitch?

the decibels of a sound wave
the frequency of a sound wave
the wavelength

Explanation:

• Decibels measure the intensity (loudness) of a sound wave, not pitch.
• Wavelength is related to frequency ($v = f\lambda$, where $v$ is the speed of sound, $f$ is frequency, and $\lambda$ is wavelength), but it is the frequency of a sound wave that directly determines pitch. Higher - frequency sounds have a higher pitch, and lower - frequency sounds have a lower pitch.

Answer:

the frequency of a sound wave