The correct answer is D. All the above.
Good quality stones must be durable, free from clay, and resist the action of acids.
Durability is the ability of a stone to withstand wear and tear. This is important for stones that are used in construction, such as for countertops or flooring. Stones that are not durable can crack, chip, or fade over time.
Clay is a type of soil that can cause problems for stones. Clay can absorb water and expand, which can cause the stone to crack or break. Clay can also contain minerals that can react with the stone and cause it to discolor or deteriorate.
Acids can damage stones by dissolving the minerals in the stone. This can cause the stone to lose its color, become pitted, or even crumble.
Stones that are durable, free from clay, and resistant to acids are the best quality stones for use in construction or other applications where they will be exposed to wear and tear.