I just took the test and the answer was: They added more detail to distant objects!
Hope this helps
 
        
             
        
        
        
Answer:
C
Explanation:
Stippling is just doing a bunch of dots
 
        
                    
             
        
        
        
The answer is the horizon line. 
 
        
             
        
        
        
Okay, so my answer gets deleted because I used the word I believe. Fine then. I hope you failed whatever quiz this was for
The answer was scale by the way.