Answer:
I'm pretty sure it's B because I studied this topic and I'm not right I'm sorry.
<span>Audible beats are formed by the interferences of two waves in which are from the slightly different frequencies which is letter a. It is because having two waves that consist of slightly different frequency causes or produce the audible beats to be formed in which they are beats that causes sound to be either loud or soft.</span>
Answer:
$v_f = = 7.9 \times10^3 \text{ m/s }$
