Prove that the frequency of beats is equal to the difference between the frequencies of the two sound notes giving rise to them.

A) The frequency of beats is given by f beats=∣f 1−f 2∣, where f1 and f2 are the frequencies of the two sound notes.
B) Constructive and destructive interference between the two sound waves result in the phenomenon of beats.
C) The perceived sound intensity is maximum when the frequencies of the two sound waves are close.
D) All of the above