Codon is three DNA and RNA nucleotides that go to a certain amino acid and or stop certain protein signal during synthesis
Hope this helps :) 
        
             
        
        
        
When we breathe, our respiratory system takes up oxygen and carbon dioxide or other useless gases go out . The oxygen combines with the haemoglobin in the blood of the circulatory system . This is transferred to all the cells of our body to get energy.
        
             
        
        
        
Answer:
The cell structure is the plasma membrane also known as the cell membrane. 
Explanation:
The plasma membrane is the thin coat of lipids (phospholipids) that surrounds and encloses a cell, also can be called the cell membrane 
 
        
             
        
        
        
Because electrons are “pulled” towards the oxygen.
        
             
        
        
        
<em>I think the answer is C, Hence I would pick the answer to be B because it sounds to be more information into the answer then A/B. Hope this helps, let me know if I am right. </em>