Answer:
A undercarriage with four or six wheels at the end of a railroad car 
Explanation:
I hope I helped 
 
        
             
        
        
        
i believe its c cause i got that one right
 
        
             
        
        
        
Since narcolepsy is a chronic sleep disorder that causes overwhelming daytime drowsiness, it usually results in overwhelming drowsiness. So, a cause could be not getting enough sleep. 
 
        
             
        
        
        
Doing anything else, I guess