They are examples of precipitation
        
                    
             
        
        
        
Answer:
By the process of cellular differentiation which consists of physical and functional changes of the cell used by processes at the genetic level. The expression of these in each type of cell is different. That is to say that the type of cell follows at a time of development there is differential activation of some genes and repression of others
 
        
             
        
        
        
I think the correct answer from the choices listed above is the second option. The enzyme pepsin that is present in the stomach denature in the intestine due to the alkaline environment of the intestine. This is because pepsin has an optimum pH that is very low which is ideal for the acidic conditions of the stomach. 
        
                    
             
        
        
        
Because they are made mostly or partly out of gas.