What Are the Main Characteristics of Soil Above a Limestone

Multiple Choice

What are the main characteristics of soil above a limestone cavern that leads to the formation of a cover collapse sinkhole?

A) thin enough that it can trickle through limestone cracks into a cavern below
B) sandy and loose enough that it can trickle down into cracks in limestone
C) coarse-enough grains that surface water can percolate down into cracks above a limestone cavern
D) fairly well cemented so it can maintain the roof of a cavern
E) thick, clay-rich, and cohesive enough to develop a large cavern before it collapses