Answer:
C. Vaccination 
Explanation:
vaccination is the administration of a vaccine to help the immune system develop protection from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. 
 
        
             
        
        
        
Keeping constant the number of chromosomes of the species and perform a summary of recombination, through crossing-over 
( Swapping – increases the <span>genetic variability )</span>
hope this helps!
        
                    
             
        
        
        
I believe the answer is hormones. correct me if i'm wrong.
        
             
        
        
        
Heterotrophs, primary consumers, and herbivores..