Kenneth observes that as an ambulance approaches him, the pitch of the sound of the siren is higher, and the pitch decreases when the ambulance moves away from him. Which of the following is the possible scientific reason for the situation?
A The wavelength of the sound wave gets shorter, and hence the pitch gets higher
B. The wavelength of the sound wave gets longer, and hence the pitch gets higher
C. The wavelength of the sound wave does not affect the pitch
D. The wavelength of the sound wave changes the speed of the wave