48. Why does blood turn dark red as it circulates through the body?
(a) It starts to clot.
(b) It gets old and dirty flowing through the
body.
(c) The oxygen in it is replaced with carbon
dioxide.
(d) The farther blood is from the heart, the
more dark red it is.

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