Concept:In limestone caves, mineral deposits that form sharp pillars hanging from the ceiling are called stalactites.
Explanation:Stalactites develop when calcium carbonate-rich water drips from the roof of a cavern and leaves behind mineral deposits.
These deposits gradually grow downward, forming pointed pillars that hang from the ceiling.
In contrast, stalagmites build upward from the cave floor.
Dolines and uvalas are surface features of limestone regions, not hanging roof pillars.
Therefore, the correct term for sharp pillars hanging from the cavern roof is stalactites.
Answer:D. Stalactites