Correct answer only !

an ambulance has its sirens on as it travels down the road. the dog in front of the ambulance will hear a sound since the waves are pushed together in front of the car.

An ambulance has it's sirens on as it reavels down the road. The dog in front of the ambulance will hear a higher pitched sound since the waves are pushed in front of the car.

B. higher pitch

Higher pitch

Explanation:

From Doppler's effect we understand that when a source of sound approaches a listener, the apparent frequency perceived by the listener is higher than the actual frequency of the source. And the pitch is directly related to frequency. Higher the frequency, higher is the pitch.

Thus, when the ambulance with the siren on approaches the dog in it front, the dog would hear a higher pitch sound since the waves are pushed together in front of the car which means number waves per unit time increases which means frequency and hence pitch of the sound increases.

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.