The correct answer is
C) Tailings
Explanation;
Tailings are the byproduct substances which are left over from mining during extracting of resources, such as extracting of copper or gold from ores. These tailings include finely ground rock particles, ranging from sand-sized to silt-sized.Toxic chemicals are used to extract the valuable materials from the ores which remain in the tailings at the end of the process. Theses tailing may leach out into ground water producing pollution.