They have hard shells that preserve.
Two different types of succession—primary and secondary—have been distinguished. Primary succession occurs in essentially lifeless areas—regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier.
I believe that C is the correct answer because Photosynthesizing animals are autotrophs and they can photosynthesize on their own which would make all of the other answers untrue
