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 :( )
The seeds fly everywhere so therefore it is logical
a central vacuole is a cellular organelle found in plant cells
It is inapropriate because the administration of too much antibiotic alters or destroy the functioning of the pancrea
