Sinkholes can form when

A rainwater containing carbon dioxide dissolves underground rock

Explanation:

Water in an underground rock is groundwater. Underground water can also erode and deposit material. Rainwater absorbs carbon dioxide (CO2) as it falls down to the surface. The CO2 groundwater creates landforms by getting rid of rock.

they are known to reach a speed of 21 miles per hour

the atmospheric gas that forms a mild acid when dissolved in water is called carbon dioxide. the correct answer is a. 2.) chemical weathering would cause an inscription on a marble headstone to become harder and harder to read over time.