Answer:
The wavelength of the sound the person observes will be longer than it was, and the frequency will also be lower than it was.
Explanation:
From Doppler effect we know that
[tex]f_L= f_0(\frac{V-V_s}{V+V_0})[/tex]
f_L= frequency observed by the listener
f_s= frequency of the source
v= velocity of sound
Vs= velocity of source
Vo= velocity of observer
so
when the Source( car siren) moves away, Vs increases and the factor (V -Vs)(V +V_0) decreases
thus f_L also Decreases
option C it is