Answer: Vestigial structures
Explanation: Vestigial structures are an anatomical feature or behavior that no longer seem to have any purpose in the present form of an organism in the given species. Usually, they are often parts of the body that used to preform important functions in earlier forms of the organism.
Phytoplankton and Photosynthesis
Importance in Global Ecosystem
Ok, I'm not fully sure but answer B sound right, so I think it's right
Did you mean limestone? if so, then yes. limestone is a sedimentary rock.