Which best describes the relationship of the embryo and the fetus?
the embryo and the fetus are both formed when the sperm and egg fuse.
the fetus differentiates into the embryo and the placenta.
the embryo has more cells than the fetus has.
the fetus is more developed than the embryo.

The diagram below shows the layers of a rock having a trilobite: a rock column labeled rock is shown. the column has three layers. the bottommost layer of the rock has one shaded rhomboid shape, the middle layer has a rhombus with a diagonal along with two identical organisms marked as, trilobite, in the key, the top layer has two semicircles. a key is shown on the right side of the diagram. the shaded rhombus is marked as a, the rhombus with the diagonal is marked as b, the semicircle is marked as c which statement about the rock fossils is true?