Answer: Tides are periodic rises and falls of large bodies of water. Tides are caused by gravitational interaction between the earth and the moon. The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon. 
 
        
                    
             
        
        
        
Answer:
Density =mass/volume 20/10=2
 
        
             
        
        
        
Answer: A. Two waves have a displacement in opposite directions 
Explanation: