I found the attached image on the internet related to this question.
The solid arrows represent neuronal communication. The stimulus, the effects, and the flow of information is all done by receptors and synapses that send a signals across the body in order to have effective feedback responses promoting the homeostasis of the organism.
 
        
        
        
A scientific hypothesis is an educated guess that is made about an observation based on the prior knowledge of the scientist. Hypothesis are always testable.
An hypothesis can be tested through experimentation and it can also be tested through deductive methods.
        
                    
             
        
        
        
Answer - Ground water erosion is a type of carbonic acidic water. That goes into the holes thru the soil and pretty much cracks thru rocks.