Apolice car is parked by the side of a highway and its siren emits a sound measuring 750 hz. as you approach the police car from a distance, you hear a change in the sound. the change is in the sound's

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.

D) pitch and frequency.

i don't know that i agree with that but what's the question ?

305.7

explanation:

density =m/v

density =917/3.00

density = 305.

approximately = 305.7

in four significant figures