A. after having cowpox they where immune to smallpox HOPE THIS HELPS
        
                    
             
        
        
        
Answer:
D) Expressed in the stomach, but not in the cells of the small intestine
Explanation:
 
        
             
        
        
        
Answer:
Blood, the heart pumps oxygen-poor blood to the lungs to be oxygenated. 
Explanation:
:) Merry Christmas! 
 
        
             
        
        
        
Answer:
The answer is D- Dose-response relationship
Explanation:
A dose-response relationship is an association between dose and incidence in which an increasing level of exposure will either lead to an increase or decrease of an incident or outcome. For instance, in the scenario given the dose or exposure will be the time the infants are put to bed prone while the response is the level of incidence of SIDS (Sudden Infant Death Syndrome).
 
        
             
        
        
        
Answer:
Natural selection. 
Explanation:
Natural selection is when organisms who are most adapted to their environment survive and pass on their genes while those with "unfit" genes die and don't get the chance to reproduce! This slowly creates a population that is most well suited to their habitat. Hope this helps again LOL! :)