Answer:
They propel the plot of a story.
They release tensions in a story.
They occur when characters feel uncertain about what they want.
Explanation:
I have seen this question on quizlet
 
        
                    
             
        
        
        
A human
crawls then walk then has a cane
 
        
                    
             
        
        
        
Become an astronaut. You'll see that it's round.