Most underground caves are formed by the action of water on rocks. In nature, there are many forms of terrain, which are formed in the mountains and plateaus, These types of landforms are considered to have been formed in the past. And each of these forms of terrain, which has many characteristics and features of its own.

Most underground caves are formed by the action of water on rocks.
At the time when rain water falls, there is a state of interaction or mixing between water droplets with carbon dioxide that is present in the atmosphere surrounding us, And then these drops fall on the ground, After this mixing, the drops move from rainwater to the soil and then to the ground in the way of many paths that are formed by the action of water.

question answer: Most underground caves are formed by the action of water on rocks.

Granite.
calcareous;
sandy;
oily;

The answer is: limestone rocks.