The last common ancestor of all bilaterians is thought to have had four hox genes. most extant cnidarians have two hox genes, though some have three hox genes. on the basis of these observations, some have proposed that the ancestral cnidarian's were originally bilateral and, in stages, lost hox genes from their genomes. if true, this would mean that

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?