Which Is Not a Reason That Fresh Water Wells near Coastlines

Which is not a reason that fresh water wells near coastlines abruptly become salty and unusable?

A) As water is pumped from the well, the freshwater runs out and leaves only the salty water from the sea.
B) Salt water is denser than fresh water, so it lays on the lower part of coastal aquifers.
C) Sea water infiltrates underlying pore spaces, making ground water beneath the sea floor salty.
D) As water is pumped from the well, the saltwater part of the aquifer flows up because of decreased aquifer pressure.