In a ring species gene flow occurs between neighboring populations of a species, but at the end of the ring populations don’t interbreed.
        
             
        
        
        
Answer:
Cause: Dropping the egg
Effect: The egg breaks
Explanation:
Assuming there is no comfort for the egg when it reaches the ground or surface you're dropping it on, the egg will break. The egg breaks because you dropped it 4 feet, making the effect be the broken egg. 
 
        
             
        
        
        
There was two of the same question, but here is the answer again with a little more depth.
D - spine alignment and foot size.
It was only the late Australopiths that had an S-shaped spine. This allowed for them to be bipedal, that is, the ability to walk on two legs as we do. This is because the S-shaped spine allowed them to balance when they were standing. The late Australopiths also have shorter and less flexible toes. These smaller, but sturdier feet made pushing off the ground much easier - aiding in their bipedalism. 
        
                    
             
        
        
        
<span>conceptual model is the answer </span>