Which process causes wells on land to become saline, making them unusable for drinking water? A. Erosion B. Echo sounding C. Eutrophication D. Groundwater infiltration

Answer: Option (D)

Explanation: Groundwater refers to the water that is present below the earth's surface and are obtained from the rainfall or other surface water that percolates deep down through the rocks. This process of percolation of water through the rocks and getting mixed up with the groundwater is known as the infiltration process. it is directly dependent on the porosity and the permeability of the medium.

This water when percolates through the rocks carries different minerals, such as salt, that ultimately mixes with the groundwater. Also when groundwater flows over the rocks like halite, it dissolves the salts, thereby making the groundwater salty and not usable for drinking purpose.

Thus, the correct answer is option (D).