Soil liquefaction occurs when
a. seismic vibrations have no impact on topsoil.
b. seismic vibrations pollute the entire atmosphere.
c. seismic vibrations cause the ground to act like a liquid.
d. seismic vibrations impact only the inner core of earth.

The correct answer should be C. Seismic vibrations cause the ground to act like a liquid. This is easily testable and you can even do it in your own house. If you shake a jar full of sand and simulate seismic vibrations like an earthquake, you will see that the ground in a jar or sand or anything similar will behave more like liquid than like solids.