Gastroesophageal Reflux Disease (GERD) ...
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Answer:
D. They rented farmland from white landowners.
Explanation:
 
        
                    
             
        
        
        
The enzyme pepsin functions with a very low pH of around 2. It is found in the stomach, with the acidity coming from the hydrochloric acid present there. it breaks proteins into amino acids.
        
             
        
        
        
A dam is a structure built across a stream or river to hold water back. Dams can be used to store water, control flooding, and generate electricity.
        
                    
             
        
        
        
Constants never change. 
Controls typically don't change or they are done by standard means
(like in an experiment where you water plants with sodas, the plant you use water with is the control)
Dependent variables are the outcome of the experiment. This is the result of changing something. 
Independent variables are what you are testing. A independent variable is something that is  intentionally altered.
easy way to remember it is that dependent variables depend on what other variables are. so you cant change a dependent variable, but you can change the other variables.