The correct answer is D.
As you can see, the exponential function grows by doubling the previous output with each increment of the input: start with 1, you double it to get 2, then you double it to get 4, 8 and so on.
On the other hand, the linear function adds 7 with each step. This means that the exponential function will eventually reach and pass the linear one, and will definitely be grater from that point on. In fact, if we continue the table, we get

and you can see how the exponential growth is much faster than the linear one.
 
        
             
        
        
        
55 + 80 + 95 + 100 +115 +90 =535 actual enrollments. 75 + 80 +85 +90 +95 + 100 = 525 predicted enrollments. 535 - 525 = 10 residuals.
        
             
        
        
        
Your answer is 38 I hope its correct :)
        
                    
             
        
        
        
I believe it is C hope it helps