The three things that are necessary are power, a force, and movement in the opposite direction of the applied force.
        
                    
             
        
        
        
Answer:
You could put sheet metal lining the bottom or something similar to that
Explanation:
 
        
                    
             
        
        
        
It is either A or C.  i hope i could help. if not im really sorry
        
                    
             
        
        
        
It is a reflecting telescope and a compound microscope. I know this for sure