The two correct answers regarding the possible consequences of a lower water table are:
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Land subsidence - As water is pumped out of the ground, the support that the water provides to soil and rock can decrease, leading to sinking or settling of the ground.
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Saltwater intrusion - A lower water table can allow saltwater from oceans or seas to flow into freshwater aquifers, contaminating the groundwater supply.
So the correct responses are "land subsidence" and "saltwater intrusion."