A listener is at

When the source of sound moves towards an observer neither the frequency of the sound nor the amplitude of vibration of the particles changes. The velocity of sound is also not dependent upon the speed of the source. Hence the options A, B and D are not true.
In such a case, only the apparent frequency of the sound to the observer increases because the same consecutive phase of the sound wave is received earlier hence the wavelength of the sound towards the observer decreases. Thus option C is true.