As you approach the police car with blaring siren, you hear a change in pitch and frequency. The apparent pitch changes as a result of the Doppler effect. Frequency determines pitch; frequency and wavelength are inversely proportional. You wouldn't "hear" either one. The result is pitch.
The correct answer would be frequency, intensity, and amplitude.
It can be explained with the help of Doppler effects which states that the frequency or wavelength of sound changes (increases or decreases) as source and observer move towards or away from each other.
Due to this effect, the frequency and intensity of siren increase as we move towards the siren.
In addition, amplitude also increases as we move towards the source of the sound and decreases as the observer moves away from the source.
D because it has the lowest wavelength, meaning the wave is the longest. Its crest are more spaced out creating lower energy. The smaller distance between the crests equals the higher the sound. Creating higher energy.
I am 95% sure this is right. Very sorry if it isn't. Hope it helps. ;3
