Sinkholes can form when

a. rainwater containing carbon dioxide dissolves underground rock

b. the water table rises due to flooding

c. minerals dripping from a cavern ceiling form stone pendants

d. streams drop sediment as they enter lakes

Sinkholes can for when:
A. Rainwater containing carbon dioxide dissolves underground rock

Water in an underground rock or sediment layer is groundwater. Underground water can also erode and deposit material. Rainwater absorbs carbon dioxide (CO2) as it falls. The CO2 groundwater creates landforms by dissolving away rock.