Diabetes is my final answer
        
             
        
        
        
Virus is the only organism which has only one strand
        
             
        
        
        
Answer: because they are situated near aquifers
Explanation:
Aquifers is a underground layer of rock which can hold and release water in desirable amounts so petroleum industries claims the well are safe.
 
        
             
        
        
        
They use a internal pouch which is named swim bladder. 
Explanation; Oxygen will enter a fish’s mouth, and passes through their gills. The oxygen will be taken and gets carried by hemoglobin through their bloodstream. Hemoglobin will take out some of the oxygen into their swim bladder. The amount of oxygen will show if they will sink or rise. Your question is how do they rise. If he goes up too much, the meaning of this is when the gas diffuses into their blood and out the gills. 
Got this from a writing, but rephrased it.