D. rift valleys.
Trenches occur at convergent oceanic plates; fossils are extremely old bones, bodies, or footprints, which have gotten so old the intervening years have turned them into rock; U-shaped valleys are valleys which are shaped like the letter U, and are usually formed by glaciers, which tend not to occur underwater very often. 
        
             
        
        
        
They are top producers of diamonds
        
             
        
        
        
The movement of the sand parallel to the shore is call long shore drift I learned this in school but if I got it wrong I’m so sorry but it’s good enough that I tried to do it and help you
        
             
        
        
        
Life could be different after an ice age because the ice would melt and form large boundaries of water. The land would not be the same at all.