Choose the word which is different from the rest.

The answer is C. Cliffs.

Lapies, stalactites, and stalagmites are all features of limestone caves. Lapies are small pits or holes in the limestone that are formed by the dissolution of the rock by water. Stalactites are icicle-like formations that hang from the ceiling of a cave, and stalagmites are cone-shaped formations that grow up from the floor of a cave. Sinkholes are large depressions in the ground that are formed when the limestone bedrock collapses.

Cliffs are not features of limestone caves. They are steep, vertical or overhanging rock faces that are formed by the erosion of the land.