changes in which property are heard when the doppler effect occurs?\npitch\namplitude\nvolume\nwavelength

Brief Explanations:

The Doppler - effect for sound is perceived as a change in pitch. Pitch is related to frequency, and the Doppler effect causes a change in the frequency of the sound waves reaching the observer when there is relative motion between the source of the sound and the observer. Amplitude is related to loudness, volume is a subjective measure related to amplitude, and while wavelength changes in the Doppler effect, what is heard is the change in pitch (frequency).

Answer:

A. pitch