Concept:Limestone regions undergo chemical weathering because rainwater, made slightly acidic by dissolved carbon dioxide, slowly dissolves the rock.
Explanation:Rainwater absorbs carbon dioxide from the air and forms weak carbonic acid:
CO2+H2O→H2CO3.
This acid reacts with calcium carbonate present in limestone.
The chemical reaction is:
CaCO3+H2CO3→Ca(HCO3)2.
Calcium hydrogencarbonate is soluble in water and is removed in solution.
This slow dissolving of limestone by acidic water is known as solution weathering or carbonation.
It is the most common weathering process found in limestone regions.
Answer:D. solution