Answer:
Limestone.
When carbonic acid seeps through limestone underground, it can open up huge cracks or hollow out vast networks of caves.
Step-by-step explanation:
This is the process of chemical weathering.
This is the chemical reaction between Carbonic acid (H2CO3), i.e. Acid Rain, and the Limestone (CaCO3), i.e. Calcite. The product of this reaction is Calcium Bicarbonate Ca(HCO3)2, which is soluble and is washed away by the rain.
...
Hope this answer can help you. Have a nice day!