Which of the following statements are true?

A.)Primary succession begins in an area that did not have life before.

B.)Secondary succession ocurrs in an area that already had life and soil.

C.)Primary succession begins in an area that does not have soil.

D.)all of the above are true

Crinoids, also known as sea lilies, appear to be sea plants but are not plants at all. crinoids are an echinoderm species which uses anchoring structures called holdfasts to attach themselves to the sea floor. crinoids were most abundant in pennsylvania during the mississippian period, which ranged from 375 to 320 million years ago. fossils of the crinoids shows that during most of this time pennsylvania was that provided favorable conditions for crinoid growth. a) glacial terrain b) a dry and sandy plain c) mostly mountain ranges d) covered by warm, shallow seas