Answer:
Beats are the difference in frequency.
(a) is correct option.
Step-by-step explanation:
Beat :
Beat is the difference of the frequency of two waves.
The difference in frequency is equal to the number of beat per second.
Amplitude :
Amplitude of the wave is the maximum displacement.
Frequency :
Frequency is the number oscillations of wave in per second.
Intensity :
Intensity is the power per unit area.
Hence, Beats are the difference in frequency.