Normal settlement and shifting debris, vibrations, and aftershocks can cause secondary _____ and previously accessible voids to become inaccessible or can eliminate the void spaces altogether.

• A. Collapses
• B. Deformations
• C. Shifts
• D. Crumbs

Answer: (A)

The key idea is that debris after an initial collapse can remain unstable and subject to further failure. Normal settlement, shifting debris, vibrations, and aftershocks can produce secondary collapses, which may fill or close previously accessible void spaces. This means an area that a rescuer or victim could reach can suddenly become inaccessible or disappear altogether as material further collapses into the void.

Why the other ideas don’t fit as well: deformations describe shapes changing but not necessarily ending the usefulness of a void; shifts imply movement without the specific failure of supporting material; crumbs isn’t a technical term for this context.