It mimics the movement of the waves 
        
                    
             
        
        
        
The first choice on the list is the correct one.
 
        
             
        
        
        
Assume that the small-massed particle is  and the heavier mass particle is
 and the heavier mass particle is  .
.
Now, by momentum conservation and energy conservation:
    
    
Now, there are 2 solutions but, one of them is useless to this question's main point so I excluded that point. Ask me in the comments if you want the excluded solution too.
    
So now, we see that  and
 and  . So therefore, the smaller mass recoils out.
. So therefore, the smaller mass recoils out.
Hope this helps you!
Bye!
 
        
             
        
        
        
Answer:
This was my best estimation of the answers
 
        
             
        
        
        
The metal conducts the heat, which makes cooking easier.