In Order for Limestone to Collapse to Form a Major

In order for limestone to collapse to form a major sinkhole, the ground above must be ____.

A) thin and porous so that rainwater passes through easily
B) small-grained so the soils can percolate through fissures
C) thick and rich in cohesive clay to allow a cavern to form
D) high in peat, allowing decomposition in the presence of oxygen
E) acidic, to speed the dissolution process