Differing physical forces is the correct answer :)
        
                    
             
        
        
        
Answer:
D. it will expand and become a red giant.
Explanation:
In the main phase of any star's life, hydrogen is being fused into helium inside the core. This phase takes up 90% of the star's life span, and this is the phase the sun is at now. The next phase is where it turns into a red giant. Once the hydrogen has completely turned into helium, the inert helium ash collapses on itself. Which in turn causes the core to get denser and heat up, which also expands its size. It appears red because outer surface is a lower temperature, that makes it appear red (hence the name "Red Giant")
 
        
             
        
        
        
Explanation:
A. They would surround an animal and drive it off a cliff. 
B. Groups would hide in trees and shoot arrows when an animal was near. 
C. The tribe would circle an animal and scare it until the trauma made it fall over. 
D. One tribe member would lure one of the large creatures away from rest, and the entire tribe would attack it. select the best
 
        
             
        
        
        
I think it might be chemical