Headphones should be constructed so that when you play music the volume has to stay at a safe level meaning you can't control it so people don't blow their ear drums. Some people may like their music loud and others not so much so it wouldn't be fair if they couldn't control how high or low it goes.
        
                    
             
        
        
        
C is a given statistic, and a pertinent point. Out of all the answers I feel as if it's the strongest. 
D and E are also answers that add value to the role of the self-driving car.
A and B don't claim anything about the value of a self-driving car and are just observations.
 
        
             
        
        
        
i need a passage to help you
 
        
             
        
        
        
The underlined word isn't there.... 0-0
        
             
        
        
        
i do not understand the question can you explain?