Sickle-cell disease is common in tropical and sub-tropical regions because being a carrier, carrying a single sickle-cell mutation (sickle cell trait), affords some resistance to malaria.
        
             
        
        
        
Photosynthesis and respiration work together by creating the energy and transporting it. 
The process are similar because they both take something in, and let something else out. 
The processes complement eachother by Respiration being able to take oxygen to the leaves, and the leaves using that oxygen to power their chemical reaction. 
Good luck there friend!
 
        
             
        
        
        
Answer:
I think is C.
Explanation:
Oh and the mouse is not cute.
 
        
                    
             
        
        
        
Answer:
From The School of Biomedical Sciences Wiki. Complementary base pairing is the phenomenon where in DNA guanine always hydrogen bonds to cytosine and adenine always binds to thymine. The bond between guanine and cytosine shares three hydrogen bonds compared to the A-T bond which always shares two hydrogen bonds.