Answer: The correct answer is "A musical instrument is in tune two sound waves with very different frequencies interfere".
Step-by-step explanation:
Beats are produced when the different frequencies of two sound waves interfere.
When the two sound waves of different frequencies approach our ear then there will be alternating constructive and destructive interference causes sound loud and soft.
Therefore, the correct answer is "A musical instrument is in tune two sound waves with very different frequencies interfere".