When the source of sound moves away from a stationary listener, there is an apparent

Explanation

The correct answer is that there is a decrease in the frequency of sound when the source moves away from a stationary listener. This phenomenon is explained by the Doppler Effect. As the source moves away, the sound waves are stretched, leading to a lower frequency and thus a lower pitch. This is why the correct option is 'decrease in the frequency of sound.'Option A is incorrect because the pitch, which is directly related to frequency, decreases rather than increases. Option B is incorrect because amplitude is related to loudness, not frequency or pitch, and is not affected by the movement. Option D is incorrect because if the frequency decreases, the wavelength increases, not decreases.