Draw the sound waves for a low-pitched and a high-pitched sound. Write one use of ultrasonography. Which wave property determines pitch?

(N/A) The diagram shows the wave shapes for low-pitched and high-pitched sounds. $A$ low-pitched sound has a lower frequency (fewer waves per unit time),while a high-pitched sound has a higher frequency (more waves per unit time).
$(b)$ Ultrasonography is used for the medical examination of the foetus during pregnancy to detect congenital defects and growth abnormalities.
$(c)$ Frequency is the wave property that determines the pitch of a sound.