The karst topography is formed by the actions of

Ground water

Explanation:

Karst topography is formed when the underground water breaks down the bedrock into soluble rocks. Hence, the bedrock of Karst topography is made of soluble rocks such as limestone. There is no surface water and topsoil in this topography and hence, the water from rains become part of the groundwater.

the answer to your question is tooth decay.

that would be called plucking : )

explanation:

''plucking, also referred to as quarrying, is a glacial phenomenon that is responsible for the erosion and transportation of individual pieces of bedrock, especially large "joint blocks". as a glacier moves down a valley, friction causes the basal ice of the glacier to melt and infiltrate joints (cracks) in the bedrock."