What are beats? A. periodic fluctuations in the velocity of sound waves B. periodic fluctuations in the wavelength of sound waves C. periodic fluctuations in the intensity of sound waves D. periodic fluctuations in the frequency of sound waves

The answer is

C. periodic fluctuations in the intensity if sound waves.

D. periodic fluctuations in the frequency of sound waves

Explanation:

Beat is referred to the phenomena that occurs when to sound waves interfer with each other and they have different frequencies.

This difference is what creates a beating, wich in sound waves manifest as high and low sounds, this as a result of the oscilating frequency.