Final answer:
A person on the bridge would hear the pitch of an air horn during a bungee jump become lower as the jumper descends and higher as the jumper ascends, due to the Doppler effect.
Step-by-step explanation:
During a bungee jump, if someone is blowing an air horn, a person on the bridge would experience a change in the perceived pitch of the sound due to the Doppler effect. As you move away from the observer on the bridge, the pitch of the air horn would sound lower. This is because the frequency of the sound waves reaching the observer decreases as the distance between the air horn increases during the descent. Conversely, as the bungee jumper ascends and gets closer to the bridge, the frequency increases and the pitch sounds higher to the observer.
The correct answer to the question is:
a. The pitch would get progressively lower (i.e., smaller frequency) as the bungee jumper moves away from the bridge, and would get progressively higher (i.e., larger frequency) as the jumper ascends back towards the bridge.