Architects and sound engineers routinely use sound-absorbing materials on ceilings and walls. In addition, they have sometimes tried to create optimal acoustics by building the ceilings and walls of concert halls with rippled or (i) $$\qquad$$ surfaces, so that the sound is reflected and (ii) $$\qquad$$ at many angles.

Blank (i)	Blank (ii)
A. invariably rigid	D. distorted
B. highly polished	E. diffused
C. slightly undulating	F. auditory