16. the spreading of sound waves around openings in barriers is called
a. reverberation.
b. an echo.
c. diffraction.
d. refraction.

C. diffraction
Diffraction by description is occurrence where the sound wave is interrupted or interacts with certain obstructions or barriers. According to Huygens-Fresnel principle, it is where the waves are interfered by said circumstances during its travel in the confined specific space. Furthermore, the amount of size the wavelength is directly proportional to its interacted slit or barrier thus, these behaviors and amount are positively correlated. Moreover, it occurs in a variety of waves –may it be sound waves, water waves or electromagnetic waves.