D sediment lowers oceanic ph
        
                    
             
        
        
        
Answer:
a series of pools built like steps to enable fish to bypass a dam or waterfall.
Explanation:
A fish ladder, also known as a fishway, fish pass or fish steps, is a structure on or around artificial and natural barriers to facilitate diadromous fishes' natural migration. 
 
        
                    
             
        
        
        
Dependent should be the control variable