Answer:
You are correct it's the earth! 
Explanation:
The reason why is because, the term "elliptical orbit" is used in astrophysics and astronomy to describe an oval-shaped path of a celestial body. The Earth, as well as all the other planets in the Solar System, follow this type of orbit around the Sun. The shape is created by the varying pull of forces, such as gravity, on two objects, such as the Sun and a planet.
Hope this helps! :)
 
        
                    
             
        
        
        
Answer:
The most closely related are amphibians and reptiles.
The least related are amphibians and mammals
Explanation:
Amphibians broke off from reptiles, birds, and mammals around 260 millions years ago and next up are the reptiles which broke off around 225 million years ago. So they are the most closely related
Mammals are the last to break off, around 200 million years ago. So they are the least related to amphibians.
 
        
             
        
        
        
The immune system. 
The immune system acts as a defense system of the body. It fights against bacteria, viruses and any other disease causing pathogens. Some chemicals can weaken the immune system and make them vulnerable.
        
             
        
        
        
Answer: Closed
Explanation:
At  resting membrane potential( RMP) sodium channels remained shut, this is because , previously  in depolarisation,the  voltage  gated sodium  channels  were opened for sodium to diffuse  into the Axon. However   these channels closed  after reaching their refractory period,s.
Therefore a  change  in the extracellular concentration of sodium will not  open them