Answer:
The correct answer would be option D.
Explanation:
Large natural reservoirs or source of water below the surface of the Earth is known as the aquifer. The aquifers have become badly polluted because of several reasons, especially human-caused water pollution. But there are few natural processes too that pollute it and make it very unsafe.
Some rocks have toxic metals like mercury and arsenic in them. If such toxic metals get dissolved in water they will make water toxic and lethal.
Thus, the correct answer would be option D.
