Question

Is groundwater contaminated by sewage from a ruptured septic tank can sometimes be naturally purified by flowing for a relatively short distance through a _ _ __.

Answer 1

Answer:

sandstone aquifer

Answer 2

The choices can be found elsewhere and as follows:

sandstone aquifer 
fractured limestone aquifer 
cavernous limestone aquifer 
spring where the water table intersects the ground surface 

I think the correct answer is the second option. Groundwater contaminated by sewage from a ruptured septic tank can sometimes be naturally purified by flowing for a relatively short distance through a fractured limestone aquifer.