An echo is an example of the type of wave interaction called

Explanation:

There are many types of wave interactions i.e. reflection, refraction, diffraction, interference etc.

An echo is an example of the type of wave interaction called reflection. It follows the laws of reflection. A sound wave strikes a surface, it strikes the surface and reflect back producing repeated sound called echo.  

Hence, echo is an example of reflection of sound.

your answer is c! hope this : )