Choices 1, 2, and 3 all emit carbon dioxide, not enough to destroy the planet, but they still can cause it over a large amount of time, due to Carbon Dioxide being a greenhouse gas. Therefore, the answer is 4. Bicycles do NOT emit any carbon dioxide at all.
        
             
        
        
        
Answer:
The circulatory system
Explanation:
The heart, veins and arteries works together to service the cells of the body