The diagram illustrates the movement of sound waves between an observer and a race car. As the race car drives away from the observer, notes that the sound from the car gets quieter and the pitch lowers. Which statement is the MOST plausible question the observer might ask to explain the phenomenon she experiences?
A. Why does the sound of the engine change as the car drives away?
B. What is the effect of the change in speed of the car and the pitch of the sound?
C. What is the relationship between the volume of the sound and the pitch of the sound
of the car?
D. How do changes in frequency and amplitude affect the pitch of the sound generated
by the car?