Answer :
The limestone caves of Kentucky and New Mexico were formed by the chemical weathering of limestone by carbonation which is a true statement. So, the correct choice is (a) True.
Limestone caves are typically formed through a process known as chemical weathering which occurs when water containing dissolved carbon dioxide (CO₂) forms a weak acid, called carbonic acid. This acid reacts with limestone, primarily composed of the mineral calcite (CaCO₃), causing it to dissolve over time. The dissolution of calcite results in the characteristic features of karst topography such as caves, sinkholes, and underground streams. Limestone deposits themselves are often derived from the remains of marine organisms like corals and clams that produce structures made of calcite. The carbonation process that forms limestone caves involves the precipitation and deposition of CaCO₃ from water as the solution becomes supersaturated when CO₂ gas is released upon warming. Groundwater containing atmospheric CO₂ dissolves CaCO₃ and forms microscopic cracks in the rock which eventually enlarge and form caves. Over long periods, ranging from tens to hundreds of thousands of years, the continuous action of flowing water and the deposition of CaCO₃ leads to the formation of stalactites from the ceiling and stalagmites from the floor of these caves.
