Irk look it up on the computer
        
             
        
        
        
Answer:
The human respiratory system contains the organs that allow us to get the oxygen we need and to remove the waste carbon dioxide we do not need. It contains these parts: two lungs. ... various structures in the chest that allow air to move in and out of the lungs.
 
        
             
        
        
        
The answer is that it gives them shelter
        
                    
             
        
        
        
Answer:
Carbon dioxide, Oxygen
Explanation:
The circulatory system of our body works following two pathways -
In pulmonary pathway the deoxygenated blood is carried to the lungs while in the second pathway, known as systemic pathway, the oxygenated blood is carried to the various parts and organs of our body. Thus the completed sentence in the question will be -
Blood being pumped by the heart is circulated in two circuits. One circuit carries blood with high levels of carbon dioxide to the lungs, and the other circuit carries blood with high levels of oxygen to the body.