What do we get when two sound waves of slightly different frequencies interfere with each other?
a. resonance
b. beats
c. standing waves
d. first harmonic

B. Beats

Explanation:

When two sound waves of slightly different frequencies are superimposed at a point in the space then the amplitude of resultant wave will change maximum to minimum cyclically with time.

This phenomenon of changing amplitude of sound with time is known as Beats.

So here we will have

now we have

so this above equation is for the BEATS

explanation:

could i give you a exaplo that could you?

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.