Answer:
Ten arms! Hope this helps!
 
        
                    
             
        
        
        
Not sure if I'm correct but my best guess is the cell membrane seeing as it surrounds the cell itself and is responsible for allowing certain molecules to diffuse in or out of the cell. Good Luck! :)
 
        
                    
             
        
        
        
Answer:
Oceanic crust is denser than continental crust. At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust. (Sometimes, oceanic crust may grow so old and that dense that it collapses and spontaneously forms a subduction zone, scientists think.)
Explanation:
 
        
             
        
        
        
Answer:
sodium can form an ionic bond with fluorine
Explanation:
fluorine is f ;)
this happens because the sodium atom needs to lose an electron so the fluorine electron can join and create the bond. 
 
        
             
        
        
        
Answer:
The alveolar walls and capillary walls share a membrane. That's how close they're getting. This allows oxygen and carbon dioxide to readily pass from the respiratory system to the circulation. Oxygen molecules bind to red blood cells as they return to the heart.