I think it's D. Sry if you get it wrong though
        
             
        
        
        
Answer:
<h2>an organism in which both copies of a given gene have the same allel is homozygous. </h2>
 
        
                    
             
        
        
        
Because bacteria mutates that's why we have a new flu vaccine every year , because strains of DNA in the bacteria change all the time.