Physical weathering is the mechanical breakdown of a rock, but the composition remains the same so the color and texture should not change. Chemical weathering requires a reaction that changes the chemical composition of the rock. The answer is d. It is a basic definition of a mineral. Shale is made up of clay, so soil made from this rock does not drain well.
Limestone contains calcium carbonate, a base.
Therefore it will dissolve when acidic rainwater flows through it, creating caves. Sandstone contains many pores that are of various sizes that can filter out groundwater pollutants, but they are well connected so that water will flow through them at a useable rate. It does not contain high levels of harmful minerals, and does not readily weather. Therefore, it is the rock in KY most likely to produce a drinking well with clean, safe water. Shale contains clay and is in small, thin layers.