The frequencies at which standing waves are made are called frequencies. a. constructive b. destructive c. interference d. resonant

The frequencies at which standing waves are made are called RESONANT frequencies.

Explanation:

When frequency of source and the frequency of the pipe is equal then we will observe the condition of resonance in the tube

So this is the condition of formation of standing waves in the pipe

So here we can say that

The frequencies at which standing waves are made are called RESONANT frequencies.