B. Bicarbonate
<em>The blood brings bicarbonate to the lungs, and then it is exhaled as carbon dioxide. The kidneys also help regulate bicarbonate... it is excreted and reabsorbed by the kidneys.</em>
<em>The body's main response is to get rid of more carbonic acid and hold on to as much bicarbonate base in the kidneys as it can.</em>
 
        
             
        
        
        
In general, the term organelle is used for the small structures within a cell.
 
        
             
        
        
        
The simple microscopic organisms the only life forms on earth was 560 million years.