Answer:
The proton gradient produced by proton pumping during the electron transport chain is used to synthesize ATP. Protons flow down their concentration gradient into the matrix through the membrane protein ATP synthase, causing it to spin (like a water wheel) and catalyze conversion of ADP to ATP.
Explanation:
 
        
             
        
        
        
Well I don't know.  Let's actually LOOK at the picture and see if that helps.
A,  B,  C,  and D all have the same TOTAL length, but  A  has the most waves crammed into that same total length.
By golly, that means the length of <u><em>each</em></u> wave in  A  must be shorter than each wave in  B,  C,  or D. 
The correct choice is <em> A </em>.  Looking at the picture did the trick ! 
 
        
             
        
        
        
It would be both speed and direction depending on the man's swing 
        
             
        
        
        
The beach boys i think.. if not im sorry
        
             
        
        
        
Please find attached photograph for your answer. Please do comment whether it is useful or not.