In the context of the Doppler effect, if the stick figure is stationary and a sound source (like a vehicle) is moving towards the figure, the stick figure will experience a higher pitch sound due to a higher frequency. Conversely, if the vehicle is moving away, the stick figure would experience a lower pitch sound due to a lower frequency.
Since your question does not specify the direction of the sound source, if we assume the sound source is approaching the stick figure, the correct answer would be:
c. Higher pitch sound due to a higher frequency.
If the sound source were moving away from the stick figure, the correct choice would be:
a. Lower pitch sound due to a lower frequency.
But based on the most common interpretation (approaching source), "c" is the appropriate choice.