Concept:Karst regions are mostly made of limestone, and the most important weathering process there is carbonation.
Explanation:Rainwater absorbs carbon dioxide from the air and soil to form weak carbonic acid:
H2O+CO2→H2CO3This carbonic acid reacts with calcium carbonate present in limestone:
CaCO3+H2CO3→Ca(HCO3)2The calcium bicarbonate formed is soluble in water.
It is easily dissolved and removed in solution.
Over time, this chemical weathering creates caves, sinkholes, and other Karst features.
Thus, carbonation is the key weathering process in Karst landscapes.
Answer:D. Carbonation