Concept:Sharp, slender rock formations that hang downward from the roof of a limestone cave are called stalactites.
Explanation:Limestone caves contain dissolved calcium carbonate.
Water dripping from the cave roof deposits this mineral slowly over time.
These deposits build downward as slender, pointed structures.
Because they grow downward from the ceiling, they match the phrase "downward growing pinnacles."
Stalagmites, on the other hand, grow upward from the cave floor.
Therefore, the correct option is stalactites.
Answer:D. stalactites