I think the answer is "the older it is"
Reason: I might be wrong but is something (like a shell) gets buried in something (like sand), overtime many things (like dirt, soil, sand, etc.) will be on top of the original. This will make layers. So, the older rock is on the bottom since it has been there for the longest and it gets covered by other stuff (causing the layers).
Hope this helps! :) (If I'm wrong, sorry :( )
<h3>Playing the role as ” procoter of the help beads ”, the sea otther is able to mantian a balance of the ecosystem , naturally by conusiming sea urchins ...</h3>
<h2>I hope it is helpful for you....</h2>
The answer is D its tightly packed cells allow for proctection against harmful substances.
